I will stay away from the lock/pre-lock part of the discussion, because it's my hope that my comments and experience will help the OP and not derail the thread.
The seven shot 686+ has a different double action trigger stroke than the typical Smith & Wesson K and L-frame (six shot) guns that I grew up on. It's noticeably different and without pulling punches, I hate it. The 686+ just gets my goat because it looks like the gun I know so well but it doesn't operate in a familiar manner.
In the 686 vs GP-100 decision, I'd choose the 686, and it would be close.
In the 686+ over the GP-100 decision, I'd so very much choose the GP-100 and have zero regrets.
I'd take an old, used 686 over a brand new, never touched 686+, and I'd happily pay more money for the older gun. I'd take any K-frame magnum over any 686+.
In my own opinion, finding an extra shot (from 5 to 6 or 6 to 7) is definitely a draw to a defensive or carry revolver. But in a medium/large frame revolver that you would use as an all-around fun shooter or an outdoorsman's tool? Give me the six shots and the proper amount of meat between chambers on that big, beautiful cylinder.
Attention Brass rats and other reloaders: I really need .327 Federal Magnum brass, no lot size too small. Tell me what caliber you need and I'll see what I have to swap. PM me and we'll discuss.