Both. As crap as that sounds, there's room for both in my life.
15mm came about as I went through a period of restricted living space and a budget. It was a faff getting the armies together as dedicated 15mm VSF ranges were (not sure if they still are) restricted. Saying that, it was easy to adapt colonial ranges and indulge in some kitbashing. Eventually got there though.
Terrain was another matter, there was nothing on the market for a 15mm 19th century London or English urban setting. Blue Moon have a range, but they aren't cheap if you're in the UK.
28mm is just..…….. sexy!
Being a part of a massed 28mm scale game is great.
Either way, I've had good games with both scales.
Sorry James, that's probably as helpful as tits on a bull