Strictly better? No.
One of the major points of Disguise Self is that it can not only alter your appearance (via illusion), but your clothing and equipment as well.
It's important to note the inverse of this: Alter Self does not specify that it modifies your clothing or equipment. This means that, depending on how severe your alterations are, you may no longer fit into your armor and your clothing may clearly no longer fit you, depending on how simulationist your DM is on the topic. This is especially important if using the "Variant: Equipment Sizes" rule on PHB p.144:
In most campaigns, you can use or wear any equipment that you find on your adventures, within the bounds of common sense. For example, a burly half-orc won’t fit in a halfling’s leather armor, and a gnome would be swallowed up in a cloud giant’s elegant robe.
The DM can impose more realism. For example, a suit of plate armor made for one human might not fit another one without significant alterations, and a guard’s uniform might be visibly ill-fitting when an adventurer tries to wear it as a disguise.
Using this variant, when adventurers find armor, clothing, and similar items that are made to be worn, they might need to visit an armorsmith, tailor, leatherworker, or similar expert to make the item wearable. The cost for such work varies from 10 to 40 percent of the market price of the item. The DM can either roll 1d4 × 10 or determine the increase in cost based on the extent of the alterations required.
Even if your equipment does fit you after the effects of the spell, any well known gear or accessories may still let you be identified, especially if they're more well known then your actual physical attributes.
There are a few other considerations as well.
One of them is that both Alter Self and Disguise Self can be used at the same time, to enhance the illusion with actual physical changes underneath it. Do note that this is only possible because Disguise Self does not require concentration, which is another point in its favor over Alter Self, which does. This means Alter Self can fail earlier than intended (especially in combat or while under stress), while Disguise Self will last the duration under most conditions, and still allows you to cast other concentration spells.
Another is comparing how Disguise Self and Alter Self interact with height & size.
Alter Self actually changes your height, while Disguise Self only creates the illusion of a height change, keeping you your usual size. This might matter if your DM actually cares about character height in certain situations rather than just your size.
In addition, Alter Self restricts you to only changing your appearance to a creature of the same size with no other restriction on maximum height gain/loss, while Disguise Self only has a restriction on height change rather than size change.
For example, with Alter Self, you could change the shortest possible dwarf into the tallest possible goliath, whereas with Disguise Self, you could make a dwarf appear to be a halfling (so long as you're not trying to change your height by more than a foot in doing so).
Overall, I'd probably rate Alter Self better than Disguise Self in some combination of the following situations:
- There is plenty of time to make preparations in advance, including having an appropriate alternate outfit ready.
- You are unprepared, but you only need minor superficial changes with no drastic change such as size, making the lack of alternate costume not an issue.
- You are in no danger of having your concentration broken for the next hour, nor are you likely to need to cast any other Concentration spells.
- You are likely to be thoroughly inspected for some reason or another.
In other situations, there is a chance Disguise Self may be the more appropriate spell. In a situation requiring an emergency drastic appearance change (clothes, size, and all), for example, I would much prefer Disguise Self as my option.
Realistic Likeness
This is a supernatural effect, thus no saving throws are allowed, and it has no duration. The bonus remains in effect until you decide to remove it.
Does not allow you to change the appearance of your equipment.
You could try to change your creature size, with a -10 on the check.
Kitsunes naturally recieve a +10 Disguise bonus to appear human (and not kitsune-y), so unless you want to mimic someone's exact appearance, this feat is unnecessary.
And finally, you should check with your GM if this feat allows you to change into anyone or just humans, as this changes the usefulness of this feat completely, like the Editor's note says:
The text of this feat states that you can mimic an “individual” which you have encountered, but it likely should specify that Kitsune have the ability to turn into humans, so GMs are encouraged to read the feat as follows: “You can precisely mimic the physical features of any human you have encountered…”
Disguise Self
This is a magical effect that works as a spell, and the save DC is based on your Charisma modifier, plus one for being a 1st level spell (thus DC 11+cha mod). Anyone who touches you, is allowed a Will save to disbelieve the effect, removing the Disguise bonus.
As a spell-like ability, it has some advantages over the actual spell. It has no verbal, somatic, or material component, nor does it require a focus.
It's important to notice that this does not change the sound your equipment does if you decide to change their appearance, so you could make your full plate look like a dress, but it will still clank when you walk on it (which also allows a Will save).
So, unless your Charisma is really high, here and then someone will disbelieve your disguises, because the save DC won't scale with your character class levels.
It also has a duration of 10 minutes per caster level (which is your HD). So at most, it will last for a few hours.
Using Both
Yes, those two abilities can help each other, Realistic Likeness grants a circunstance bonus, while Disguise Self grants an untyped bonus. So if you happen to be using both abilities at once, you could recieve up to +20 on your disguise check as long as both are to appear exactly like a specific individual.
Again, these bonus ALSO should stack with your Change Shape's ability bonus, as it is a racial bonus, as long as the form chosen is that of a human. Which is why you should check with your GM regarding that Editor's Note.
Detect Magic
People casting Detect Magic are your bane. All three abilities are magical in nature and will ping when someone casts Detect Magic around you. Though Disguise Self is the only one they can identify with a Spellcraft check, the others will at least show up as a magical effect on your character, which will raise suspicion.
Best Answer
Generally, the number and position of limbs should match. Beyond that it's up to the DM.
Disguise Self has similar wording:
But there are no strict rules about what "body type" means.
We can assume that shapes with a different number of limbs -- a centaur or a xorn or a marilith demon -- are definitely not possible. And presumably (assuming humanoid targets) both seeming and disguise self can produce the forms of other humanoids.
But there are a few other cases that might obtain, and it's up to the DM to rule in these cases:
Quadrupeds. Animals like wolves (as mentioned in the question) have limbs with the same number of joints at the same general positions on the torso. So an argument could be made that they have the same "basic arrangement of limbs" as a humanoid. Contrariwise, an argument could be made that arms are not the same as legs, or that plantigrade legs (like humans and bears have) aren't the same as digitigrade legs (like a canine or feline has). This is really a DM call; the intent of disguise self seems to be that such forms are not ones the spell can produce; with seeming it's not so clear.
Tails. Are tails limbs? Can a tiefling hide their tail with disguise self or seeming? Can a humanoid without a tail use seeming to appear like a lizardfolk, with a substantial tail? Here we have a Sage Advice rulings:
(source)
From this we can assume that limbs that don't have any game effect aren't considered for this purpose.
If I were DM in this case, I would rule that seeming (and disguse self) can't cause humans to appear as quadrupeds, and that those spells can't hide (or produce) a tail that functions as more than a cosmetic detail.