No loyalty to filters. It is mostly about price with an eye on the quality as well (but not fanatical).
My Scion has only had OEM (first 4 changes from the dealer) and Wix (2 Wix and 3 Wix made CarQuest Blue), but only because I got a great deal on them. I have a few Fram ToughGuard, Bosch D+ and a Mobil 1 filter in the stash for it as well.
My truck I have used Fram, Purolator, Bosch, Supertech, and EcoGard.
For now I plan on using OEM for my Santa Fe, but only because I can readily find the OEM for cheaper than most aftermarket.
Motorcycle has had Supertech, Bosch D+, OEM, and ToughGuard, with a few TG and an Ultra in the stash for it. This is probably the only vehicle I will be really picky on filters with, I plan on buying only Ultra's in the future once my stash is used up.