Well I just bought a Puma, and I have shot a marlin before so here is my 2 cents.
1. LOOKS- you like the Puma but not the wood, but wood can be changed or refinished. You don't like the resever on the Marlin, you can;t do much about that.
2. FUNCTION-- I love the action on the Puma the Marlin is good too, but I think the Puma is smoother.
3.ACCURACY-- I can't say much about the accuracy on the Marlin, never really shot one that much for groups. For the Puma in 45lc that I owen and have only shot 30 rounds of Black Hills cowboy loads in it, the accurcy is great, and should get better as it breaks in and I start handloading for it.
4. VALUE-- I think there both pretty close but you can find good deals on the Puma.
I would say find a Puma, I think they look better and shoot great. As soon as I buy a pair of Vaquero's I'm going to buy another Puma in 38/357