I'm mostly fond of my 4" Henckel's 4 star paring knife (same brand as my chef's knife).
Some jobs are too small or too detailed for a chef's knife. I sometimes use both knives on the same item (large hunks of meat in particular) for the same job.
While small, garlic chops great with a chefs knife. But please don't make me julienne a pepper without my nice sharp paring knife.
I also have a 3" knife that I don't like so well, but my husband likes more than me. So I can't say 4 inches is right, just right for me.
Go to a knife store and play with some lengths, then maybe try that in the brand you like (as is your chef's knife).
Nancy