What is the best sized work hook for medium sized bass

I tend to fish for large sized bass myself...usually a 3/0 Owner wide gap hook for me....

Since you asked about Senkos in your other question, I assume that is what you are asking about here. 3/0 is the size for the best action from the bait. If that isn't what you are asking, not sure what you really mean? I have caught bass up to 5lbs on a #6 split shot drop shot hook.

Depends on the size and or thickness of the bait for me. I'm not using a small hook on a big ole thick bait,.

4/0

^^^ what he said.
there is no such thing as best. shank size depends on the length of the bait, gap size depends on the thickness.

this

I use anything from 3/0-7/0 depending on the bait

A 4/0 should be a good number for most baits

A 3/0 for a 6 inch worm, a 4/0 for a 7 inch worm. a 5/0 -6/0 for the 8-10 inch is what I have read in a good detailed book.

Simple as that^^^

You may consider a straight shank or an off-set shank also.
Make sure you use a good quality hook! I like Owner.