I dive the Oceanic VT3 (which is the Aeris T3) and my wife dives a Galileo SOl. The SOL is wrist mount only and I haven't run across any aftermarket ways of making it retractor friendly. The T3 and the SOL are both great computers and have the same basic features: wireless AI, DTR, EDT, cute bars and graphs, enough user adjustable alarms to piss-off every fish in the ocean, etc. The SOL is much more conservative than the T3. The T3 can work with multiple gasses if you're a tech diver, but the SOL kills it in the coolness factor. I also tend to lose my transmitter signal more than the SOL. But, the SOL is also HUGE. Since you're comparing an $800 computer with a $1500. one I'll assume $ is not really a factor and I say get the one you want. Your LDS would have a hard time making a convincing argument that the T3 is better than the SOL. Less expensive. . . Yes. But definitely not better. Either way, you really can't go wrong.
The digital compass on the SOL is accurate, maybe a little too accurate. It can be a pain to use at first since it seems to jump around a lot and can be hard to get settled. It just takes a little getting used to, but once you do it's just as easy to use as a regular compass and seems as accurate. I use a regular compass and the wife uses the SOL and both of us manage to keep the team on course.