I'm sure the Tartan is the better boat, but I have yet to see a single Tartan 30 for sale here in the bay area or nearby.
I'm also looking to own the boat primarily for liveaboard, with occasional bluewater cruising. Not so much for daysailing. That being said, one of the big reasons I like the Vanguard is the headroom, as I'm 6'2". I haven't been able to find info on the Tartan 30 in that respect, although I think I remember the Alberg has 6'2".
When you say the Vanguard were "not great boats", do you mean in construction, or in sailing responsiveness/speed?