You shouldn't use F bait. Why is that? I have 5 reasons.
1. You can't get rares 2. You can only get one large per bucket 3. You catch mostly junk 4. You can KILL rares with it (seriously) 5. When you use A bait, it can increase your fishing reputation
Oh, and I use A bait, and un-degraded F bait, sometimes D bait.