its really up to you. i have had all the geo models (except sl91 and the gsl) and each one has shot great. the geo+ was just a geo with the gst and gr2 installed already, the geo 2.1 changed the location of the pcv and had the pops and angled reg collar- shot the same as the geo2... the geo 3.1 shoots the same as the geo 3, it just has the new sl4 reg, front grip and at pipe and grips. personally i feel the 3.1 is more comfortable than my geo 3 was, with that said i played all season with my lv1 and i was used to that and the geo 3.1 felt perfect as soon as it picked it up. its really up to you...do you have to have the newest out there in the geo3.1 or the geo3 that shoots the same?