Difference entre different systeme guitar synthé !!!

http://www.thegearpage.net/boa(...)synth

Roland GI-20 - is expressly a guitar midi interface box + usb at about $399
Roland GR-20 is the current 13-pin compatible synth box with general midi + Roland poly synth sound at about $499 (sans pick-up)
Roland GR-33 is this a better sounding, more feature rich, discontinued version of the GR-20? Apparently the samples are better quality in the GR-20 and one would hope the tracking was better.

Axon AX-50 is a midi box + usb + general midi + some synth $499?
Axon AX 100 MKII is the original, more sound feature packed unit at $699

The word on the street is that Axon tends to track better while Roland GR's offers better sound from the box. Is this true? If one were more focused on using a midi guitar to control software instruments in Garageband, it would seems the Axon AX-50 could be a wise choice over Roland's GI 20 based on apparent tracking superiority and at least some sonic ability of its own. Axon speaks of a 32-bit RISC chip to enhance its responsiveness. That said, one could add a $40 standard 5-pin midi I/F to use the midi out of the GR-20 into a computer.