Regarding Galaxo:
- that ROM is optimized Android 1.6 in other words Donut, fastest ROM available for Galaxy. The only down side is that almost no-one is developing for Android 1.x.
Regarding GAOSP:
- my suggestion is that you go for GAOSP-2-PUBLIC-BETA-3 (highly recommended), Froyo Android 2.2.2 based, all is working fine, many apps to choose from the Market (developers are developing for android 2.x and higher). Down side is speed and responsiveness of the device aka dialer lag (to little RAM installed on it). But try to see if it matches your taste. There is also some optimizing you can do O/C the unit, using swap (you will need micro SD card with class 6 as minimum), compcache,...
About GAOSP 3 (use the nightly version, cause it was released later then PUBLIC-BETA), based on Gingerbread but it has is some issue regarding Camera, also it seems that it deletes camera firmware. So if you don't use camera, you can go for it - but it uses more memory then Froyo (your choice).
Verdict: try Froyo first and Gingerbread later. Use Zeam launcher to save memory. About Dialer lag, can't help there. Apparently, after reboot it works instantly but later it's starting to lags (you can always try Dialer 2 or something).
p.s: get your latest Google Apps from
Cyanogenmod - for Froyo use ver.6 (MDPI) and for Gingerbread ver.7
Hope it helps.