Have you pushed the Prowler on grass and at the gym? What is the difference on the resistance?
I've pushed it on fake turf in two different gyms, and on asphalt on a recently paved street, and on asphalt in a badly-patched parking lot. Here's what I think of those:
Parking lot - the prowler moves more easily until it hits a rock and lodges into place. Lots of foot slippage because you don't get a lot of traction.
Street - smoothest ride for the prowler, a little bit of foot slippage.
Turf - the gym I work at has somewhat slippery turf. The prowler really bites into the turf, but my shoes don't, so I can't push it very heavy before my shoes are the weak point and I slip instead of push.
At DeFranco's they have really good turf. It really bites into the prowler's skids hard, so it's a bitch to push. But you don't slip, period, so you have all the traction you need to push it. The combination means the prowler is heavier (more traction) but you can load it up because it's the limit of your leg strength, not slipping or falling on loose rocks or getting stuck in ruts in the road, that holds you back.
That's why I can barely push the prowler with 1 plate on each horn at my work gym, but I can run the prowler with 3 plates on each horn at DeFranco's...yet even a few months ago 2 plates on the asphalt outside was too much. My legs could push it, but I couldn't get enough traction to really drive into it.
Does that all make sense? I haven't tried it on real grass...yet.