More than just a trimmed down GR-55
I bought a GR-55 as soon as it came out, and have been a big fan. When the GP-10 was announced it seemed to me like a stripped down GR-55 in a smaller package. How wrong I was. True, the GP-10 loses the GR-55's two PCM synth blocks, the looper and the MFX block. It also has 99 user presets instead of 297. But the remaining features have been updated and improved, and in some cases, expanded. And the GP-10 adds a powerful new synthesis block, a harmonist, a string bender, the ability to combine alternate tunings with a 12 string guitar, and more. The GP-10 adds a second built-in control pedal, expandable either to 4 CTL pedals or 2 EXP pedals. I added a Boss FS-7 to give me 4 CTLs, which provide great foot access to the features. The GP-10 is also much more powerful and flexible than the GR-55 for assigning features to buttons/pedals.
The re-amping feature is great for recording. The editing software is powerful and intuitive, and allows for sharing presets with others. It also makes the 99 preset memory less of a limitation, as you can create and save as many live sets as you want.
Another huge plus for the GP-10 is you can access all the amp and effect models without a 13 pin connector. I have been bypassing the amp block and just using the GP-10 effects in front of my tube amp with great results. So the GP-10 is great for direct-to-PA with a GK guitar or a regular guitar, and a great front end to a guitar amp.
Features aside, the GP-10 just sounds better than the GR-55. Less noise, and just better overall sound quality. The COSM models have been refined and are more responsive feeling and realistic sounding. In particular, the new COSM amp models sound great, and the old ones have been significantly improved (and I thought they were good before). While I was able to coax good sounds out of the GR-55, great sounds just seem to leap out of the COSM models in the GP-10.
I will still turn to my GR-55 when I want the PCM synths. Otherwise, I'm moving on to the GP-10.
The big letdown is lack of CoreMIDI compliance. Let's hope Boss/Roland get on board here with an update.