I'll weigh in.
I think that BOTH are a good idea! And, as much as you'll hate me for saying it, I genuinely think you should make both. Maybe even separate games built on the same engine. I absolutely LOVED TF2. I loved how balanced the gameplay was, and how each class had an antithesis. I loved how defeating the other team required not only good skills, but good cohesion as a team. I can't tell you how many hours I spent scouting as a spy, feeding info to a heavy/medic or soldier/medic team.
On the other side, I'm currently playing through Privateer again, and it's really awesome! My only wish was the the ship classes were a little more estranged from each other (moreso than already), and that the game didn't lend itself QUITE so heavily towards the mercenary route. Hell, even the merchant guild usually offered 50% bounty missions. I'd really enjoy mapping out cargo routes and making lists of prices, keeping a mental tab of where I've probably sated the marked with my wares so that I need to haul somewhere else for a while, and choose different suppliers.
Anyway, all of that to say that I love both ideas, and I think they both merit exclusive attention, either as separate games, or two different modes of the same game. Keep up the good work, man!