The GTS is a bit more nimble and it definitely feels sportier than the S in the corners. Turn-in is much better than on the S so Porsche have done some rather noticable tweeks to the chassis and it's not just lowerd with -10/-15mm (depending on if you go with Air Suspension or not). The 20hp/40nm performance increase is there, but the chassis difference is what is most noticable. At least after my testdrives back-to-back. The GTS is more about aesthetics and if you like the blacked out look (black badges, black spyder wheels, GTS logos on head rests, black alu-interior, etc). And also if you either way would pick the options that already come standard on the GTS compared with the S (Sport Exhaust, bigger wheels, more interior leather, PASM, upgraded lights, to name a few). Should also be added that the PSE on GTS sounds a tad bit sportier/louder than PSE on Macan S/Turbo. Not something Porsche is bragging about, but there is a noticable difference both inside/outside.
Only reason for buying a Macan S Petrol is if you purchase it bare naked without options and/or don't like the black theme. Otherwise the GTS is your pick since you get lot's of options included in the price and it will also be better coming resale.
Concerning the facelif - if Porsche follow its tradition of 7 year lifecycles with a facelift after 4 year we will see the new facelift introduced in LA 2017 and first customer FL-cars delivered to customers spring 2018. Maybe someone else have more accurate infor about this.