Pinions are getting more common as now Losi , Novak and RRP make them alongside the Monster.
The Mod 1 / Mod 0.8 is a measure of the pitch of the gearing - Different cars use different pitch. Most Buggy/Truggy are Mod 1 - E-Revo/Emaxx are 0.8 (or 32p).
Personally I would get Mike's as they are super hard and prices / service are outstanding.