After owning both and daily driving them, I would say the GTS-t is a better daily. Don't discount the RB20DET so much, they are a great engine. I slapped a NEO6 turbo on mine and easily returned 10L/100km or less if I stopped boosting it so much. Car was completely stock (engine, exhaust, suspension/wheels). Very easy to live with, and even had a factory sunroof! (Type M).
GT-R, a lot more expensive to run (12+L/100km with very easy driving), parts are more expensive, it's heavier and there's more things that will go wrong (ATTESA, HICAS) mainly because all of them will be thrashed.
BUT, and this is a big one, the way the GT-R drives is on a completely different level. The GTS-t feels tail happy, but is easier to drive (lighter, smaller turning circle). You can have a quick squirt through some hills/corners without much effort and it will be fun. GT-R feels like a restrained animal. The turbos comes on hard, feels heavier, as if more effort is required to drive it. But once you're on boost and ready to move, GT-R will decimate a lot of cars and quite easily yourself. You really have to take it to track days to fully open it up, it's just far too dangerous on the streets.
If you aren't driving much everyday and have the cash to spend when required, get the GT-R. If you do a fair bit of driving, get a GTS-t with as few mods as possible. Don't get me wrong, a near stock GT-R is very reliable, same with a GTS-t. Vehicle's history obviously plays a big part.