With me it's not so much material as it is shape. Visually, the S&W targets are the most beautiful, especially when the wood is well figured. To my average size hand they are too large in the wrong place, at the bottom.
For shooting I like properly shaped (ergonomic) grips. The absolute best feel I've ever had in my hand was the palm swell K-frame combats by Fuzzy Farrant. I was/am hesitant to alter my grip frame to accomadate them. If I was carrying a gun for a living again, I would alter a 586/686 and mount a pair.
Another most comfortable "right" feel is the Pachmayr Compacts that are on my roundbutt model 19. No, they aren't beautiful, but they fit and are easy to hold even with a wet or sweaty hand. I like stuff that works, not just look good.
N-frame is a different story. Again, factory targets are beautiful, great to look at but totally wrong for my hand. Hogue's, wood or rubber, and Pachmayr's grippers suit me. I have a 625-2 that is fitted with a pair of Ahrends fingergroove that work for me. I think that gun may have a K-frame sized grip. At any rate, it feels good in my hand and is awesome to look at as well (Cordia wood, I think).
Another combination the works well for me is the classic combo of magna's (K or N) and grip adapter. I like a grip adpter and round butt guns also.
Surprisingly, I do have a pair of N-frame targets that fit me fairly well. They are rosewood, smooth and of the Coke bottle shape. From this board I have learned they are rather collectable/hard to find. They were a gift from one of my shooting mentors who has passed. Some day I will let them go to another Smith and Wesson admirer.