Well, as all Geo's should have the G-R2 kit, the difference with the Geo+ is the inclusion of the Soft Touch (ST) kit.
This comprises a bolt with a ported face, and a firing can with only one solenoid vent hole rather than six. You also get a pair of volume restrictors to limit the amount of air stored in the firing chamber.
People using Reballs with the Geo had found that at the low velocity associated with Reball use, the Geo was suffering some cycling issues, due to the HPR and/or dwell being too low. It was also found that the Reballs could seal the face of the bolt, and the vacuum created as the bolt then tried to move forward was causing the bolt cycle to choke.
This second issue was resolved by switching to a ported bolt, as it wasn't then possible for a ball to lodge in the face of the bolt. The volume restrictors solved the issue with low velocity use, as reducing the amount of air released to propel the ball allowed you to lower the velocity without having to greatly reduce HPR pressure or dwell.
As a bonus upgrade - not perhaps directly related to the Reball problem (although I guess lower bolt speed could help to prevent the vacuum building up rapidly?) - the firing can was altered to slow the acceleration of the bolt. The main purpose for this was to reduce kick and make for a smoother cycle.
Other advantages that stemmed from these design changes were that the ported bolt diffused the air hitting the ball, and the reduced bolt speed would mean lower impact of the bolt on a ball, so as well as improving Reball use, and reducing kick, the ST kit should also be softer on brittle paint.
While the ST kit was never intended to be an efficiency upgrade, and indeed, most people would see no increase in shot count from using it, some people who's stock Geo's have been particularly inefficient, have seen improvements when swapping to the ST kit.