When I ask my players what they think, the most common response I get is that they prefer subscription model because it's more fair. They hate games where the person who spends more money gets an advantage. (Of course, my sample set is biased.)
The advantage of the item-mall category is that you get great price discrimination, and you also get a much larger player base than you would on subscription only. But it's seen as cheesy and unfair, so works better with casual games, and I think that's the key.
If it's a casual game, go for item mall or freemium. If it's a more serious or competitive game, then go for subscription. I think we're seeing a lot of item mall games coming out these days because we're also seeing a lot more casual games.