Thank you for the consideration to ask us which we'd prefer.
I find that when I look up a pet it's usually because I'm trying to get information about the pet's spawn location/timer/etc.
So, for me the "General" tab would be my pick for the default tab. After all, I can't very well concern myself with battle statistics for a pet I cannot even locate.
After I get the location information I usually proceed directly to the user comments tab for the pet in question. This helps me get a feel for what other members are doing and what their experiences have been like in relation to acquiring the pet.