I have a N900 but have not used the emulators, really. However, I do know there TONS of them. I would go to Maemo.org if I was you, and look under downloads > games, but also in their "talk" forum section.
Given all what the N900 can do in addition to gaming, I would lean towards it. Especially if you can get one of the great deals on it floating around now (e.g. Nokia USA had it for $199 if you handed in an older, still reasonable Nokia phone).