Well, even though I'm head honcho, I don't know much about syncing with Thunderbird. There are 3rd party products like birdiesync (not free) and FinchSync (free) for syncing with Windows Mobile, but I'm not aware of any for Android (both there may well be something). WinMo syncs over USB but Android is designed for cloud syncing to Google and other services, so there that rules out the usual USB sync utilities and companies. HTC provides their own sync tool to sync to Outlook over USB but it doesn't support Thunderbird.
Call quality is very good with both phones and is similar (both being made by the same company and using the same network).
BTW, you can put the phone into flight mode so it doesn't ring when teaching class (assuming it's the phone calls that are disruptive and not alarms). That way you need not turn it off. Though as you noted, it does take care of that maintenance reboot regime.
Honestly, I like both phones quite a bit, so it's not easy to tell you which one to choose.