Lift capacity is the same on both. The hydraulic pump capacity for operating implements is lower at 4.0 gpm vs 5.6 gpm, but the working pressure is the same at 2050 psi.
What do you plan to use it for? Small tire size will limit lift range of three point, and 50 inch deck is not real big. Maybe these are not a concern for your applications. The big reason I bought a 755 over the 855 is the shorter wheelbase for maneuverability, and I did not want the 72 inch deck so I understand what you are saying.
Still, look ahead at what you may want to do later. I had a JD 430 L&G tractor for a few years and while I was pleased with the engine and the 60 inch deck, it became clear I needed larger tires and four wheel drive to do my work. In some ways the 655 would have been a downgrade for me. Smaller engine and smaller deck than the 430. After 17 years my 755 and its various implements such as the loader still serve me well and do all I need.
In the end though, look at all the tractors and decide what works best for you. If you want more technical details on the 655 just ask. I have all the manuals.