In purely financial terms it's still better to keep the IS. you can put an aftermarket cat just to pass inspection and it won't cost you much. Hatch struts are 100% DIY and cheap as hell. Headunit can be replaced with one from a used car or an upgraded one from ebay (pretty cheap probably). Exhaust leak can be fixed by a muffler shop for super cheap. As for rust and tires, both of those will affect the trade-in value of your car a lot and you'll have a hard time getting more than 5K. A brand new GTI will lose those 5K within the first 1-2 years in depreciation alone, and a used one will lose another 5-10K within 4-5 more years. You can literally just change the tires and the other stuff on your car, drive it into the ground, sell what's left of it for 1-2K and you'll be better off than buying the MK7.
That said, the MK7 is safer, faster, more comfortable and more fun. If you can afford the extra spending long term then go for it. I'd buy a used one with a warranty. Dealer offered warranties are not your only choice, and there are good aftermarket ones out there if you do your research and check everything it covers.
True, I'm sure they won't cost as much as changing to a newer car. But I do fear that these are just somethings that will add up and are only the start. I did do preventative maintenance with the 100k full service when I bought it as well as the notorious early 2000s Lexus tie rod issue. Plus with my new job's commute, it's just been really hard on the car... Only so much a 5-speed automatic of the early 2000s can do at today's speeds and aggressive traffic.
I never really looked into aftermarket warranties, so that will be something I'll have to consider.
I did consider lightly used 2018 GTIs that are still under their new car warranty. Pretty sure that's better than the CPO one at least, but maybe not an aftermarket one.
Personally, I'd never buy a VW that wasn't a TDI (I regret selling my '10, but VW gave me an offer I couldn't refuse) but if for some reason I was in the market for a GTI, I'd make sure it had a warranty. VW in North America seem to have a lot of electrical issues with their cars and those can be expensive to diagnose and repair.
Also, I'm not sure if the DSG tranny for the TDI is the same as their other cars, but if they are, then make sure the fluid has been changed on time and it has been maintained appropriately. I've seen quite a few DSG failures from people failing to maintain them.
I am tempted by a CPO 2015 Golf TDI wagon, especially since they're around $15k as loaded SELs. The fuel mileage is definitely appealing with the TDIs and I actually enjoyed driving around a 2015 TDI Sportwagon with a 6 speed manual that was traded in at my last job. The unfortunate thing is that I'd like Android Auto, which would be on 2016+ VWs.
I'm definitely looking to have a warranty with a GTI, though I imagine it'd be better to get the new 6 year/72,000 mile warranty than the added 2 year/24,000 mile Certified Pre-Owned warranty. I have also considered slightly used 2018 models with less than 10k miles as the warranty is transferable and I...think it's still longer than the CPO one.
As I hear, the DSG service is at 40k miles, so I'd want to find something that's well before it if I'm looking used. I'll be honest, I'm no mechanic, but I do know of a lot of specialty VW shops as well as friends in the area who work on them.
