all conforming grooves pretty much spin the same on a non-rough lie.... the biggest factor is in the rough...
i'd highly suggest you to re-think your outlook in choosing a wedge based on the "most" spin... rather my suggestion to you is to choose a wedge that has the most predictable spin. i used to play spin mill v1 / callaway md grooves / nike vr forged wedges and they actually all spun too much for me. sure its cool to have a wedge stop and zip back on a green but i can't tell you how many times ive tried to chip a shot and the ball would actually stop instead of roll out the extra foot i needed it to. i've actually switched to xft tp wedges and have holed out more holes greenside in the 2-3 years than the previous 10 years of playing....
so going back to your question of how to get an accurate feel for them in an indoor hitting bay its pretty easy. take a wedge and see how accurately you can hit a 30 / 40 / 50 / 75 / 100 yard pitch or chip. you should have a good enough swing to be able to accurately hit those to determine the best feel for a wedge. and if you cant, well then it probably doesn't matter which wedge you pick since you cant even hit a ball accurately sub 100 yards.