Demo man has seriously flawed code, but there are some updated soren chips you can put it in that help. Even brand new, the game is low value due to code and design. The left side of the game is pretty much useless, code-wise.
Funhouse is by far the better game, but overlays are absolute crap.
I'd keep your tmnt pro. You'll be losing money with either.
If you must trade, the demo man would be the better trade, especially if you can get the writer to sign it and keep it in minty shape.