The SNES version is better. The screen crunch, reduced audio quality, and washed-out colors all make this a big downgrade.

The e-reader levels are of questionable quality. It's neat to see every type of 2D mainline Mario (up to that point) crammed into the SMB 3 engine, but they should've implemented checkpoints as well. It's especially annoying for the long fortress and airship levels.

There are lots of examples of poor level design. A towering tour has one blind leap of faith that can unfairly kill you. Slip Slidin' has a bullshit moment with the penguin knockback. The all music note levels are annoying. Castle Dash has an obstacle that kills you regardless of whether you're powered up or not. It's a shoe-in has a segment where accidentally killing the enemy without pulling off a jump results in mandatory backtracking. A caped escape has a really frustrating maneuver required near the end. Bowser's Airship 2 has fire bro fireballs that can kill you from off-screen. Para beetle challenge might just be the worst official Mario level outside of anything in The Lost Levels.