A small swivel works great until the first time you or someone else reels it up to far and cracks or breaks out one of your line guides. If you are doing a carolina rig or a lindy rig it is ok cause you have the sinker there to remind you, but without that reminder one mistake can ruine your day.
A uni to uni is fast and easy on the water and there are many tournament anglers using that setup, so you know that the knot stregnth is pretty good. Mabyee not the best.
I will run a 6′-8′ leader many times on really clear lakes so that the fish can’t see my main line and also it allows me to retie my lures without having to put on a new leader all of the time.
Try different things and see what works for you.