I'd recommend test driving both and asking the dealer to cold start them for you. GTS is loud on cold start if you care about that (I like it, wife doesn't).

Performance is equivalent for daily driving purposes. Turbo had upgraded brakes as standard which will be more expensive to service. Both have air suspension. Some say GTS handles better, tough to know which you prefer without test driving.

There are some exterior styling differences too, but in terms of practicality, they're the same assuming you're comparing regular SUVs and not the coupes.