Exactly - with very few exceptions everything will run in both modes. Of course, VGA for the win!
Really? That's cool! That's the only computer I know of that does that. When you say "play better", do you mean a faster or slower framerate, or something along those lines?
You can get a utility to switch your ST between 50 and 60 Hz here, by the way. Helps some demos run better too; I use it to get some of the YM Rockerz music disks to work properly on my NTSC machine.