I like a blend of both.

I like when there are multiple gear sets at the highest level of power (more than just the 2 we normally have) all with varied stat combinations. But I also enjoy the excitement of building up to a new powerful set of equipment, too. Ideally, I think raid tiers would last about 9 months for me (with more bosses, of course), and we'd have more stats to choose from on gear, as well as perhaps 6 sets at the maximum item level (perhaps with interesting things like set bonuses and job-specific stats).