Edit: With the release of SSB4 for WiiU I must mention that the following data was collected from the 3DS version of the game. If needed I'll update, but I'm unsure if the person asking is even interested in one.
Firstly, not all Omega stages are exactly like FD in design, since FD also implies a traversable bottom part which can be used by characters like Jigglypuff and Kirby. Magicant Ω, Spirit Train Ω, and Rainbow Road Ω are examples of stages that are FD-ish in design, in fact, only Battlefield, FD, and Flat Zone 2 have pronounced bottoms.
A lot of Ω have a wall right down to the bottom blast line, though, which can be useful for certain characters that can wallcling, unlike FD. These vary in size and shapes from my personal perspective, the most notable being Arena Ferox Ω's wine glass shape, but I haven't thought up of a method to measure these accurately.
However I've personally measured the surface distances (which is what I assume your question is about) in Training Mode, by using Greninja's back crouch movement and moving from the left edge to the right, on 1/4x speed.
The following is a list of the times it takes to traverse each stage, give or take a few ms of error because of multitasking with the timer. All stages are Ω, all times are in seconds:
- Paper Mario: 23.276
- WarioWare, Inc.: 23.295
- Flat Zone 2: 23.316
- Reset Bomb Forest: 23.438
- Spirit Train: 23.442
- Prism Tower: 23.456
- 3D Land: 23.457
- Arena Ferox: 23.473
- Mushroomy Kingdom: 23.49
- Jungle Japes: 23.538
- PAC-MAZE: 23.563
- Wily Castle: 23.581
- Green Hill Zone: 23.639
- Tomodachi Life: 23.662
- Mute City: 23.682
- Living Room: 23.686
- Final Destination: 23.698
- Tortimer Island: 23.703
- Gerudo Valley: 23.709
- Distant Planet: 23.712
- Find Mii: 23.718
- Golden Plains: 23.728
- Balloon Fight: 23.735
- Yoshi's Island: 23.763
- Magicant: 23.765
- Dream Land: 23.771
- PictoChat 2: 23.775
- Boxing Ring: 23.776
- Battlefield: 23.846
- Gaur Plain: 23.849
- Brinstar: 23.854
- Corneria: 23.881
- Unova Pokémon League: 23.883
- Rainbow Road: 23.962
So I want to conclude that it is a camera illusion that makes stages look bigger than they seem. PAC-MAZE, for example, seemed to zoom in differently than WarioWare, Inc.'s.
Unmarked secret character spoilers ahead.
There is no easy way, aside from "intuitive knowledge of the character's aesthetics", to know what kind of equipment they can equip.
There is, however, a chart available on this page. It's kinda large, but here it is in text form:
- Every character can equip Brawn/Protection/Agility Badges.
- Mario: Gloves, Overalls, Shoes
- Luigi: Gloves, Overalls, Shoes
- Dr. Mario: Gloves, Tie, Shoes
- Peach: Toad, Dress, Pumps
- Rosalina: Staff, Dress, Pumps
- Bowser: Fake Nails, Shell, Dash Mushroom
- Bowser Jr.: Drill, Shell, Dash Mushroom
- Yoshi: Egg, Saddle, Boots
- Wario: Gloves, Overalls, Shoes
- Donkey Kong: Banana, Tie, Dash Mushroom
- Diddy Kong: Banana, Hat, Rocketbarrel Pack
- Link: Sword, Shield, Boots
- Toon Link: Sword, Shield, Boots
- Zelda: Magic Stone, Dress, Boots
- Sheik: Needles, Suit, Shoes
- Ganondorf: Magic Stone, Cape, Shin Guards
- Samus: Arm Cannon, Suit, Booster
- Zero Suit Samus: Beam Whip, Suit, Booster
- Kirby: Lollipop, Hat, Turbo Boost
- Meta Knight: Sword, Mask, Turbo Boost
- King Dedede: Hammer, Coat, Turbo Boost
- Fox: Blaster, Jacket, Shin Guards
- Falco: Blaster, Jacket, Shin Guards
- All Pokémon: X Attack, X Defense, X Speed
- Captain Falcon: Gloves, Suit, Boots
- Ness: Bat, Hat, Shoes
- Lucas: Bat, Clothes, Shoes
- Marth: Sword, Cape, Boots
- Lucina: Sword, Cape, Boots
- Roy: Sword, Cape, Boots
- Ike: Sword, Cape, Boots
- Robin: Tome, Coat, Boots
- Mr. Game & Watch: Torch, Watch Battery, Microchip
- Pit: Sacred Treasure, Raiment, Sandals
- Dark Pit: Sacred Treasure, Raiment, Sandals
- Palutena: Staff, Shield, Sandals
- Olimar: Pikmin, Space Suit, Boots
- R.O.B.: Zapper, Block, Booster
- Little Mac: Boxing Gloves, Clothes, Boots
- Duck Hunt: Zapper, Collar, Feather
- Villager: Lloid, Clothes, Shoes
- Wii Fit Trainer: Protein, CLothes, Shoes
- Shulk: Sword, Jacket, Shoes
- Sonic: Gloves, Ring, Shoes
- Mega Man: Arm Cannon, Helmet, Booster
- Pac-Man: Gloves, Helmet, Boots
- Ryu: Gloves, Clothes, Shin Guards
- Mii Brawler: Gloves, Jacket, Boots
- Mii Swordfighter: Sword, Jacket, Boots
- Mii Gunner: Arm Cannon, Jacket, Boots
Best Answer
Character unlocks differs between the 3DS and Wii U versions. I'm posting a complete list for both versions below. Source
Ness
3DS: 10 Smash matches or beat Classic mode
Wii U: Unlocked by default
Falco
3DS: 20 Smash matches or beat Classic mode without using any continues
Wii U: 10 Smash matches or beat Classic mode
Wario
3DS: 30 Smash matches or complete 100 man smash
Wii U: 20 Smash matches or complete 100 man smash
Lucina
3DS: 40 Smash matches or beat classic mode as Marth without using any continues
Wii U: 30 Smash matches or beat Master Core (classic mode final boss at intensity 5.1 or greater) as Marth at 5.5 intensity
Dark Pit
3DS: 50 Smash matches or beat Classic mode with three or more characters
Wii U: 40 Smash matches or beat All-Star mode on Normal
Dr Mario
3DS: 60 Smash matches or beat Classic mode as mario at intensity 4.0 or greater
Wii U: 50 Smash matches or beat one Master Order on hard difficulty
R.O.B.
3DS: 70 Smash matches or collect 200 trophies then play a Smash match or beat classic mode
Wii U: 60 Smash matches or defeat Crazy Hand after completing 10 matches in Crazy Orders
Ganondorf
3DS: 80 Smash matches or beat Classic mode as Link at intensity 5.0 or higher
Wii U: Unlocked by default
Mr.Game & Watch
3DS: 90 Smash matches or beat Classic mode with ten fighters
Wii U: 80 Smash matches or beat Classic mode with five fighters
Bowser Jr
3DS: 100 Smash matches or beat Classic Mode as Bowser on Intensity 6.0 or higher
Wii U: Unlocked by default
Duck Hunt
3DS: 110 Smash matches or beat Classic Mode with 8 or more characters
Wii U: 100 Smash matches or KO one fighter in Cruel Smash
Jigglypuff
3DS: 120 Smash matches or collect 30 different equipment items
Wii U: Unlocked by default
DLC Characters
Mewtwo
3DS: $3.99
Wii U: $3.99
Both: $4.99
Lucas
3DS: $3.99
Wii U: $3.99
Both: $4.99
Roy
3DS: $3.99
Wii U: $3.99
Both: $4.99
Ryu W/ Suzaku Castle
3DS: $5.99
Wii U: $5.99
Both: $6.99
(Note: This DLC comes with the stage as well as the fighter)
Cloud W/ Midgar
3DS: $5.99
Wii U: $5.99
Both: $6.99
(Note: This DLC comes with the stage as well as the fighter)
Corrin
3DS: $4.99
Wii U: $4.99
Both: $5.99
Bayonetta W/ Umbra Clock Tower
3DS: $5.99
Wii U: $5.99
Both: $6.99
(Note: This DLC comes with the stage as well as the fighter)