I've never stayed at either, but for your purposes, I don't think one would be better than the other except for drive time to your fishing spots. If you want to get out at night, Corpus would be the better choice.
Don't really know, I've always fished Copano or Baffin since I was young. I imagine the answer to your question depends on what you want to fish for and how you plan on going about doing it. Let me know and I'll ask a couple people what they suggest.
I've fished copano a few times and always get in the trout pretty good. I was thinking trout since the flounder run will most likely already be over. got a lil 18' skiff that I use to get out to the middle of the bay and wade.