I have to prefix this with the fact that I've only barely touched Chicken. I've been using Gambit for a few months.
Performance:
See benchmarks above.
FFI:
Gambit's is very clean. I've used this extensively, and people that are doing iPhone/Objective-C stuff with it are using the FFI. I can't comment on Chicken's FFI.
Libraries:
I'm guessing Chicken wins here. The egg system seems more developed and has more packages than Gambit's Black Hole.
Installation:
I know Gambit is painless on Linux and Mac. I can't speak to Windows nor to which Linux distros package it.
Licensing:
I have to correct you here.
Gambit is dual licensed: LGPL 2.1 and Apache 2.
Support:
Chicken's community and IRC room seem active. Gambit's are too; detailed answers are rapid on the mailing list.
Performance: See benchmarks above.
FFI: Gambit's is very clean. I've used this extensively, and people that are doing iPhone/Objective-C stuff with it are using the FFI. I can't comment on Chicken's FFI.
Libraries: I'm guessing Chicken wins here. The egg system seems more developed and has more packages than Gambit's Black Hole.
Installation: I know Gambit is painless on Linux and Mac. I can't speak to Windows nor to which Linux distros package it.
Licensing: I have to correct you here. Gambit is dual licensed: LGPL 2.1 and Apache 2.
Support: Chicken's community and IRC room seem active. Gambit's are too; detailed answers are rapid on the mailing list.