I've heard great things about Moenkopi and talked to Brady about a rental awhile back - he was prompt & professional with a quote and reasonably priced. In the spirit of competition, I'm going to recommend him for consideration on a trip I've been invited on next year. That said...
The group I went with last month got the "Painless Private" package from PRO. Total turnkey operation. Everything was very well-organized with a binder of menus that included schematic layouts of each boat and shopping lists for each meal telling what food was on which boat and in which box/cooler. The 18' boats they provided were in good condition, oar setups for each rower's choice and extra oarrights in case someone else took over and wanted to row. The gear was good, the food they provided was of good quality, pre-packed and easily prepared. We had plenty of groover capacity, & the tables, stoves, etc. were in good condition. Put-in and takeout service included a lift-gate truck with two guys to help/direct rigging/loading as needed. The Lee's crew included a former GC guide (since 1968 ) who stayed overnight and gave us Pro's own orientation, then took back any items we decided to jettison at the last minute. He saw us through our first meal with their kitchen setup, turned us over to Ranger Dave and headed back to Flagstaff with a generous tip.
Complaints - the Coleman propane lanterns they provided were a hassle to set up/take down but had plenty of spare mantles. Oh yeah, we could've used a couple more rolls of paper towels - you can decide if that was significant....
We had a very experienced core group of boaters on the trip which definitely helped things run more smoothly. Everyone with multi-day TL/planning/food prep experience was really impressed with the job they did. I'd easily recommend PRO but would also like to see how they compare against Moenkopi or REO. Compared with the brain damage associated with GC logistics, having someone else provide the gear & food like that is a reasonable deal unless you've got folks with LOTS of experience who have it all dialed in to run the show.
For food there's also Cocina del Rio: http://www.cocinadelrio.com/
I've heard great things about Karen House's food pack/prep on the Grand.
Have a good trip!