Most people here as far as I know reuse old bottles from wineries/wine bars. I have a local wine bar that saves cases of wine bottles for me. He will call/email every other week when he has about 15 cases of empty bottles. Of all the bottles, I usually end up with about 6-8 cases that I actually keep. This only because some are screw closure (I don't keep these) and the others I am beginning to learn which labels come off easier. Never, Never, Never use any cork in a screw finish bottle.
I use #9 x 1.75 corks, natural or sythetic, haven't really noticed any difference in corks yet. I am sure others will chime in with more experience.