You realize this is a contradictory statement. "Right now" gasoline and diesel fuel pricing makes gasoline more appealing. But in a "very long time," such as looking back over the past 10 years, prices are much closer overall, and the diesel's superior FE makes for a lower cost per mile. Only real question mark is durability and repair costs, and neither the new TDI or the GTI are stellar in those categories. VW's gasoline engines are far from trouble free: I saw a post from you recently recalling your B6 Passat's oil consumption.
Not picking, just mentioning that it's difficult to find the right answer. For me I'm leaning towards keeping rotary pump MKIV cars running well past middle age. And maybe my B4, too. Only thing that's hard to fight off is rust, and it sounds like it's worse up there than here. Otherwise these older cars are more economical to run, even with repair costs.
Right now, as in "I drive less than 20k km/12k miles per year", and am likely to do so for the foreseeable future as I've decided to retire early. The TSI and TDI have exactly 1 L/100 km consumption difference on the highway according to Natural Resources Canada. Plus the TSI runs on RUG. Granted a GTI needs super to give its full potential, and it runs about 1.5-2 L/100 km higher consumption.
As for diesel prices... I've been following them for the last few years. On average diesel is higher. This winter, running anywhere from 20-30 cents per liter higher than RUG. I've never seen it more than 10 cents cheaper in summer. If I factor that in, the cost per km of a TSI vs a TDI comes pretty close. Throw in the higher cost of the TDI and it starts to make little sense except for range, and resale value. However we now keep a car in the family typically for up to 15 years and 300k km, so resale is no longer an issue.
As for reliability... well the 2.0T may have consumed oil (I wasn't alone) but I lived with it. I never had to sink major $ into it, in 160k km (100k miles). However that's not been the case for my TDIs:
-MAF, coolant migration on 99.5 TDI (I actually got rid of it before the coolant migration; the subsequent owner had the problem and the car only had 80k km)
-Balance shaft module on '05 B5.5 TDI (I paid $1k, VW paid $3k)
-HPFP on '11 Golf (VW paid half)
-Intercooler on '11 Golf which didn't fix the problem.
-And now VW isn't wanting to cover rust perforation on the right rear door of our B5.5; the estimate to replace the door is $2300 (but admittedly it's nothing to do with it being a TDI, but it is part of the overall VW customer CARE disaster of an experience); I've just sent VW a demand letter threatening legal action over that one).
Bottom line I've been out-of-pocket for way more $ on my TDIs than on my 2.0T!
I might look at other brands next time around. Some of the cars on my list include a Mazda 3 hatchback, base Honda Accord (still available with 6-mt, and lots of kit for the money), Honda Fit, the new Honda HRV coming out soon, to name a few. But dang I still really like Golfs.