I have had wood grips that had finger grooves and a large thumb rest and recently, I purchased a set of Hogues.
I thought I was buying the Houge grips with the thumb rest but when I got them, they didn't have a thumb rest. I think I prefer not to have the thumb rest. The Hogues are a big improvment on the stock grips. They seem to make the gun feel lighter. I really feel like I have a hold of my MKII now.
A word of caution!
The wood grips I had were shaped like a set of Hogues with a thumb rest. They were a little fatter all around and smooth. They had the Ruger emblem in the grip panel so I assumed they were fatory Ruger grips. They were not! In fact, they were not made correctly to fit my gun. It created a dangerous situation where the gun would go off under strang circumstances. Luckly, I never had it loaded when the gun would "trip" but it was scary to know that several times, I could have shot someone in the next room if the gun was loaded while it went off. I got these grips at a gunshow so I guess I had it comming.
Make sure to use good quality grips from a known maker. Don't buy the slick looking "gun show special" wood grips like I did.