Can anyone provide me with some of the differences between Ogl WW and Sidewinder recoiled. Do you need the D20 modern to play either. I only have experience with D20 through Conan.
OGL Wild West is a stand alone product that you do not need anything else to run with it....I am not sure about Sidewinder. Both have good things about them. I would suggest getting both that way you have more to work with. If you have to get just one of course I would say get OGL Wild West....
I have both and I like both for different reasons. I'm actually running a play by post WW game using both rules intermingled.

OGL Character Creation, with Sidewinder setting/weapon stats/rules.

See my game here: