I've found that the dirt common 5/8 wave 2 meter antennas do about as well as any. I think Larson, Antenex, and several others make them, and the price is typically less than others.
Not sure what an 'M' connector is, so won't comment on them. Also find that the NMO mounts really do well, are easy to install, and are securer than others.
Don't get too caught up in the gain figures, the surroundings play a big part in that with VHF/UHF. The larger/longer 2 meter antennas take you to about the same places that a 102" whip does (2m = 7feet +/-), so that's a consideration too.
Take your pick, there's a bunch of different styles.
- 'Doc