How do the playable characters differ?

• Dash speed: How fast the character runs at full tilt with dash depressed.
• Acceleration: How long you need to run holding dash to reach top speed.
• Jump height: How far up you go after pressing jump.
• Jump speed: How quickly you rise through the air to that maximum height.
• Fall speed: How quickly you sink through the air after jumping, wandering off a ledge, etc.

Mario

• Dash speed: Average
• Acceleration: Average
• Jump height: Average
• Jump speed: Fast
• Fall speed: Average

All-around average, really. Due to technicalities, you could say his jump height is below-average - but that's only because everyone else jumps equal or higher. Hardly a bad choice to start with.

Luigi

• Dash speed: Fast
• Acceleration: Average
• Jump height: Highest
• Jump speed: Slow
• Fall speed: Slow

Reportedly a "good all-rounder". Matters are complicated by his low traction (aka friction) - don't try to suddenly stop near a ledge.

Peach

• Dash speed: Slow
• Acceleration: Fast
• Jump height: Average
• Jump speed: Fast
• Fall speed: Fastest

Also floats in midair if you hold jump (combine with the Tanooki Suit for lots of airtime). A beginner character, in my opinion - lots of room for jumping mistakes, and no risk of careening anywhere you don't want at high speed.

Toad (the blue one)

• Dash speed: Fastest
• Acceleration: Slowest
• Jump height: Average
• Jump speed: Fast
• Fall speed: Fastest

I'm not kidding about those - you have to run in circles forever to get up to full speed, and he falls like a stone. The devs apparently called him "an advanced speedrun character", which seems fairly accurate - can you say "World 3-4 in 20 seconds"?

Rosalina

• Dash speed: Slowest
• Acceleration: Fast
• Jump height: High
• Jump speed: Slow
• Fall speed: Average

Unlocked after completing World Star-2. Also, press dash for a Super Mario Galaxy-style spin attack (which, BTW, does not flip those annoying flip-when-you-jump panels (sorry folks, this isn't Galaxy)). The spin attack cannot be used with a powerup.

Captain Toad

Approved levels only.

• Dash speed: Slow
• Acceleration: Average
• Jump height: Doesn't
• Fall speed: Fast

I'll point this out again: cannot jump. (Still cutely tries to if you press jump.)

Mario - Well he's Mario, what else is there to say.

Luigi - He jumps higher, but he also moves slower as he jumps (both up and down) for better control. He also has a bit less traction on the ground.

Peach - Can float in the air by holding jump (happens before any suit's similar ability). Makes most jumps easier, but complicates timed bounces off enemies; this is irrelevant in most levels, but makes a choice couple levels very difficult. Moves slower (both walking and running), but takes less time to reach top speed.

Toad - Can't jump as high. Walks and runs faster; might take slightly more time to reach top speed, not totally sure.

Rosalina - Has the same higher/slower jump as Luigi; moves a bit slower than Peach (also reaches top speed faster). Can also use the Cosmic Spin when without a power-up by pressing the run button, which is a weak double jump and damages enemies equivalent to a paw attack. Much more effective for horizontal distance gain than vertical.

All characters seem to have equal jump height when bouncing off an enemy, wall, or trampoline. All characters have equal speed when boosted by a Boost Panel; not sure if invincible characters also run at the same speed. Movement speed affects horizontal swim speed, but jumping ability seems to have no effect on vertical swim speed.

All characters can complete all courses. Not all characters can get all collectibles, though that's mostly because some are accessed by character-specific switches; I'm not sure if it's otherwise possible for everyone to get everything.