I prefer sub just because I like know how much a game will cost, FFXIV has no nasty surprises waiting to push me to the cash shop, I pay my sub and that's it.
I may occasionally use the Mogstore but I can do this as and when I want to. It doesn't contain things that I need to continue in the game/access a certain part of the game and it's not time exclusive, so I might have an eye on a Mogstore cosmetic but wait until, say, Christmas to get it.