I'm great at 1min games and 30min games.
15 min game quality better than 5 min

If you are learning and trying to improve than I see no reason to play a fast game. I too enjoy a longer game. I can really figure out my plans, my opponents plans, possibly tactics, weak squares, so many things. But playing fast can be a great thing. You will gain much more experience very quickly. You will learn many more lines of openings, and will experience many of the lower level tactics. I would call it a personal preference certainly, but I think to play your best chess you should play a longer game. Many blitzers i know are not that great in a long game, and vice versa. I would think to be great you should do a healthy dose of both.
It seems that i appriciate playing long games than 5 mins/3 mins. Although i can beat higher rated players at fast pace games the longer ones helps me understand the game more. Is that what we call a matter of taste?