There is only one 'really good' dog in the game (who levels up to level 50): Vigilance!
The guy who sells him is still alive right now in my game, which isn't guaranteed because in previous playthroughs he's deceased (so no Vigilance).
Every time I walk by, a little voice in my head says 'buy the dog! buy the dog!' heheh... 
Don't know if he'd co-exist with my daughter's little fox though...?
I think IMO they made the default dog (ie. Meeko) unspeakably cute. 
Who could resist?
Now if only they didn't bark... constantly.
I almost killed Barbas myself, LoL 
Some guy made a mod that silenced the incessant barking.
But the dog's little dog mouth still barked...
Aaaargh! They have cut poor Meeko's vocal chords! 
It was awful (worse that the barking) so... no more dogs for me.