I would suggest a 200 providing you could find a real tidy one for that kinda money. The interiors are much nicer, there faster and they generally look nicer too imo.

Either way, you will be happy as there both cracking cars. Don't settle on your first though. ST200's and ST24's are bloody everywhere, so you will find a nice one eventually.

P.S. If you go for a ST24, make sure it's had a Metal Impellor water pump fitted. ST24's come with a plastic impellor one, and these shatter. ST200's already have a metal one though.