The major changes I noticed between the two editions are as follows:
Limits prevent characters from being overly min-maxed. Each of them is centered around an attribute that is typically dumped in normal characters; the most important attribute for the physical limit, for instance, is Strength, though other attributes weigh in they have the same impact as Strength does alone. This means that you can't build a "never gonna fight close quarters" build and just dump strength and expect to do well in other physical areas, encouraging a well-rounded thing.
Mystic adepts get a huge buff. I'm not exactly sure that this is a bad thing; they still can't astrally project, but they get the powers of both mages (other than astral) and phys-ads pretty nicely. Were they still using the BP system, this would be a flaw, and I'm not sure about allowing them as the third pick on your priority system, but I think the reason that people are upset is because they don't astrally project as much as they should when not a mystic adept.
The priority system really makes things a lot better. It prevents some of the worst cheesing during character creation (don't get me wrong-it's still possible, but you have to know what you're doing and make some sacrifices).
Combat's been changed rather heavily on the bookkeeping, but not so much the execution. The Accuracy limit keeps pistols from killing Great Dragons, which is a nice touch, but also discourages just dumping into the newly increased skills and maxing them out right away. It also makes smartlinks a more tangible advantage, as do laser sights. Armor is now a single rating for stun and physical, which makes it a lot easier for new players to understand, and, in my opinion, more realistic.
Hacking's a lot better. Mind you; the wireless thing contains some logic holes and gimmicks with the new benefits it gives stuff like cyberware or laser sights, but hackers can enjoy a target rich playground with new rules for hacking that make prepping a hacker 90% easier and playing one about 50% easier; GM'ing hacking also became a lot easier. In addition, some of the more broken technomancer stuff has been revised so you now have a reason to play a decker instead of a technomancer every single time.
All in all, it's faster and more streamlined. If you want my "reviewer" version, you can check it out on my blog, but I've said pretty much everything I said there here, only without the sales pitches.
Value Proposition
You mentioned DDI:
Even better is the WotC approach with the DDI, you can look up any
monster or item or (almost any) rule, in the most recent form, for 3
years at the cost of seven books. I think this is the way to go, even
considering the horribly slow character builder.
It's true, for three years that is a good deal. But what about for six years?
I'm still using my 3.5 PHB, ten years after I got it. I have a set of 3.5 books that is nowhere near the full quantity they released, and I'm okay with that because I don't care about a lot of the books they put out.
If DDI existed for 3.5, it would have cost me more than I paid for the books rather than less. Being an upfront cost, books don't cost more if you use them for longer. Subscriptions do.
And of course, online services disappear every day. Will DDI for 4e still be around in 10 years? If you want to play and it goes away, where did your rules go? I own a book from the 1800s, so I'm pretty confident that Wizards can't take my 3.5 paper books away should they decide it's time to move on and not pay for servers anymore (or go out of business).
Page Flipping & Sharing
I have bookmarks in my PHB & DMG. I also just know where some things are, because I've had to use them so many times. I can open the book and be in the grapple rules in two seconds. No matter how hard I try, I can't get there that fast on my iPad. I also can't have the grapple rules AND my encounter notes open at the same time with the electronic version, since my iPad can only show one thing at a time. With the books, I can put them beside each other. I can then also add a spell description from the Spell Compendium. The area around me when I DM tends to look like a book fort.
It's easy to share the book. I can hand someone my PHB so they can look up a spell description and keep doing what I was doing with my other books & iPad notes. If I have to hand them my iPad, I just lost access to everything until I get it back.
Subjective Stuff
There's a subjective side to this as well. I like how books feel. I find them easier on my eyes than ebooks. They work at the cottage, even with no power.
In the end, it's really about which trade offs you prefer to make.
Best Answer
Since most of what I have to say here is based on in person and online discussions with Catalyst Devs and Writers, you can only take this as second-hand info that I remember. I've heard discussions on message boards and talked with devs at GenCon when I could. So, again, I have nothing written down or concrete to prove this.
Dragons have, since they were first introduced to Shadowrun, been on the top of the food chain when it comes to native Earth creatures. There are other beings, such as spirits and horrors in the story-line of the SR and Earthdawn universe that make the Great Dragons worried, but as far as normal mortal creatures are concerned...oh my god, dragons.
Both in the literature and the core rule books, dragons have been put on a pedestal that not many people can knock them off of. It takes a concentrated effort to even damage a dragon, let alone kill one. And we're talking about normal dragons here. We're not even talking about Great Dragons, like Lofwyr or Hestaby. We're talking about the dragons that you will rarely see in a game. Your options, when a dragon is actually angry at you, is running as fast as you can, as far as you can, shooting the biggest guns you have, and hoping that the dragon just gets tired of chasing you and goes off to do something else.
Dragons are scary. Great Dragons are terrifying in what they can do to you. And not just you, but entire armies. In Storm Front, at least two Great Dragons were assaulted by large armies. And only one of those Great Dragons were confirmed dead. And this is after we developed weapons to act as poison to dragons and dragon kind, just so we could kill the sons of bitches. They have massive power, are massively strong, and have eternal patience. They are immortal and will simply wait you out, because your small mortal life is the blink of an eye to them. Hell, they have (rules as written) powers to straight-up nullify an edge roll of yours. They can tell fate 'No', and fate listens.
All of this goes to the point that I want to make. Drakes were pulled out of character creation because they were way too out-there to have as a PC race. While a drake is only a fraction of what a dragon could be, it's still insanely powerful and ruins their mystique of what a dragon is. If everyone can walk around being a Jedi, Jedi's would stop being cool. If everyone walks around as a drake, dragons stop having that 'out of our league' feeling you want to give to a player.
Plus, you shouldn't be dealing with a dragon anyways. ;)
(Please note that this information is through second-hand sources and I have no real vetting process for it. I have tried to write this post without blatant copying or mimicking of other opinions and thoughts.)