I have two 627's (a 2 5/8" PC and a 4" PC V-Comp) and it seems like the OP decision comes down to three issues:
1. Carrying. The N-Frames are bulkier and for a common barrel length they are heavier as well when compared to a smaller frame design. So if the OP is in a CC state (I am not), the N-Frame is not a good idea.
2. Hand size. The N-Frame 8-rounder is just bigger. I wear something between an M and L glove and it's an OK fit but the smaller 686 frame would have been better. I just happen to really like the style and the 8-shot capacity of the N-Frame.
3. Price. The N-Frames (particularly the PC - Performance Center) models are a step up in price. I don't consider it too painful but its up the the buyer.
GL,
B