I’ve played both, although it’s been a while since I played it now.
The controls are much better.
The graphics are only mildly improved. The character models are improved but they kept the same pre-rendered backgrounds of the original game, which were all made for old 4:3 screens. So on a widescreen monitor you can either have it stretched or with borders on the left and right.
I think everything else such as the audio is the same.
My partner ran into a weird bug and couldn’t progress further, but Doublefine sent me some save game files to work around the issue. I think those issues have since been fixed.