All else being the same, which would have more sparkle? I''m looking at exchanging my fiance''s ER from a typical enternity type pave, I think it''s called a fishtail, to more of a channel. The one she has is a little rough to the touch and the thickness is a little uneven.
Generally speaking, rounds will have more sparkle than princesses. However, small, well-cut princesses look very nice. My e-ring features channel set princesses. I would be more concerned with how the shape of the stones affect how they look in a channel setting. There will be visible gaps between the individual round stones, while the princess cuts can sit flush with one another.