I am getting back into the game after several years off, so I am looking at my game and tweaking a lot of things. I have been watching videos of releases at some of the top tournaments to evaluate my release. I notice a large number of the top players, especially internationally, tuck their pinky under when holding the ball. This is something which was actively removed from the games of all youth bowlers in my youth league when I was learning the game.

I'm wondering, is there an advantage to tucking the pinky, is it just personal preference, and who out there tucks and who doesn't, and why?

Old wives tale, I don't believe it does anything.

Because the tendons that controls the pinky and the ring finger work together,
(For most people, in general, you'll find it almost impossible to bend either the ring finger or the pinky without also bending the other one.)
when you bend the pinky at the 1st or 2nd joint, you are actually tightening the grip of the ring finger on the ball.

(Personally, I needed to do this when I went to a dropped ring finger span, from 5 1/8" to 5" in order to reduce the pressure on the tendonitis in the ring finger. Using the pinky to tighten the grip allowed my tendonitis to heal.)

Some coaches are of the opinion that a tucked pinky causes the hand to turn the ball early or come around the ball when you want to stay behind it, but I have not found that to be the case.

Tucking the pinky does seem to add a few revs for me; not a lot, just a few more than otherwise. It does seem to add a sense of control, for me.

As you can see it serves a different purposes for everyone. Best thing to do is a trial run for yourself. Give it a try for a few weeks or so and see how you like it.

I use it as an adjustment. If the ball is not finishing as strong as I like, I can tuck my pinkie and move one to two boards left with my feet and the ball will finish stronger. If I stand in the same spot and just tuck the pinkie when I am coming in a bit light, the ball will nose dive and split

Part of what tucking your pinky does is push the weight of the ball over to the index finger. I've tried tucking my pinky once and hated everything about it. 

However adjusting the ball weight in my hand by turning my hand over more shifting the ball weight towards my index finger did have a good positive out come without pain or other issues. It changed my pap from 5.5" straight across to 5" straight across,  and the ball has a little different rotation to it.

I do tuck the pinky I would say about 95%. I have been doing this for years with no issues. I have a stronger ball reaction when I do. The only time I would not tuck it is if the lanes are really dry and I want a tamer ball reaction.