I used the full overlap grip for over a decade, and just recently went back to regular grip or 2 finger overlap. I still drop the pinky on the bottom hand.
The overlap grip does produce more pop, but the consistency is never very good, especially when you're tired. I found that I had serious timing issues with the overlap grip, and I was often way out in front of the ball. I also tended to catch the ball too far out in front, which led to tons and tons of sidespin liners and grounders. It would literally be 1 or 2 400' bombs and 8 grounders or popups out of 10 swings. The bat comes though the zone in such a sloppy manner, and you can't really control spin very well.
I'm not saying don't use the overlap, but personally I would only use it in HR situations. Keep the regular grip for when you want to go for base hits or anything involving placement.
If you use the overlap grip full time, your batting average will probably go down 200 points. The loss of bat control becomes noticeable and irritating. You just pop up or roll over way too many balls. IMO the tradeoff just isn't worth it. The conventional grip works fine, and I don't lose that much power by using it. The conventional grip produces far more consistent results, with better timing and finding the sweetspot on the bat way more often.
The overlap grip is fun to mess with, and will probably produce the furthest batted balls of your life. At times the power feels effortless. However, IMO it's more trouble than it's worth.