I own two SYN-2 chassis along with five Synergy and three of the old Egnater modules. They sound good. But since I bought my AF3 they are all on the shelf, unplugged. Will I ever use them again? Probably. Maybe. Do they sound better than the AF3? No. They simply sound different, that's all. The Axe-FX gives me things that no tube preamp will ever give. Crazy flexibility. Great, consistent tone. Reliability. And, to top it off, it literally evolves with every firmware update and becomes a new product over time. The list of advantages is extensive and obvious.
For me lately, a big thing is simplicity- my old rig was very complex with lots of cabling including MIDI patching. Now, I have an FC-12, AF3, and monitors. It's a beautiful thing.
Latency will never be an issue for me using the Axe-FX 3 for both live and recording. I don't hear it, don't feel it. But I'm not Steve Vai, I'm just an old weekend warrior who rocks my neighborhood every Saturday night. So far no one has called the police, which means I still have something to reach for.