I own and have used a stoker and a guru on my stretch at comps. Ive won comps with both. They both perform well. I found myself not using the extra features of the stoker after the novelty wore off. The guru only has one probe so that was the only downside for me over the stoker. The stoker gets used at home and as a backup unit (and is actually for sale). The guru and a themapen pull comp duty.
Also my stretch came with a guru adapter on it. You have to pay for the stoker adapter.