I am in the middle of a project using a 3650 now. The GP PRO EX software is much better than the old Quick Designer. I still have a few hang-ups with the software. Once I started understanding how they layed out the software it is getting better. I am using it with a Banner camera (E I/P) & NTSC , MLX 1500 (DF1), ASCII display (RS 485), & CLX (E I/P). I do like the scripting features in it just to pass info.
I have not used the Red Lion yet so I can't compare them. I have used the C-More,& PV standard. They each have the pros and cons. C-More are a little light weight for the industrial world and does offer multiple protocols in 1 unit. Standard PV lack a lot of the bells and whistles some of the others do like no logging and limited to 1 protocol they are rock solid. I have they mounted on forging and stamping presses with huge shock loads and no problems. The C-Mores didn't like the shock so they are free standing after 2 failures.
If you are looking to do a single PLC with no other devices than any of them will work. Are you looking to bridge multiple protocols? If so I would steer away from the C-M and PV. The C-More will pass very limited info so it will do it just not very well.
Think of how you are going to access the PLC once you have tied up the serial port with a HMI. Does your 1500 have 2 ports or are you going to need a Pass-Thru feature? If you unplug the HMI will your system stop running or will it continue to run and the operator will just be blind to the system.