I use an R10 but don't really know why. I think it was the size and width of the rear pnumatic wheels. Other than that they are very similar. http://www.rocknrollercart.com/parts.php I load an L1 Compact, an S910, a large X-seat, an X-stand and an equipment bag. I never need to extend it. Setup and tear down are fairly simple, although the pull cable is usually what everyone complains about. It was definitely a good purchase for me; everything comes and goes in one trip.

Now I remember why I chose the R10 over the R8 - I found an online hardware store that was selling them for less that the music stores were selling the R8.