From a purely subjective point of view, I found that guns with no lug at all, (old Colts, S&W 14, 15) were more diffcult to shoot well than guns with partial and full underlugs. The Colt Police Positive MKV and Colt Diamondback (full underlugs) are great shooting little .38s, more so than the old Colts or older K38 Smiths. The partial underlugs, (S&W M19, 27 and equivalents) shoot very well for me. The L Frames and the Python also shoot very well, but not significantly better while adding a great deal more weight and changing the subjective "feel" and balance. The size of the lug is inversely proportional to the amount of muzzle flip, so if you intend on shooting really hot loads, maybe the full lug would offer a slight advantage. Since the Python, L-Frame and the GP-100 are all about the same frame size and all have the full underlug, it seems that each manufacturer came to the same conclusion on that size gun. The N-Frames are about the same weight without the full underlug and therefore, to me at least, redundant, at least in the .357 caliber.