I have an emerald cut and love emeralds but there are two things to consider:
1. You NEED to try them on. I was dead set on a cushion or oval but when I tried on an emerald I knew it was what looked best on my hand.
2. Carat size should def be a factor...a oval will most likely look bigger than an emerald, so if you are going around 2 carats the emerald would be gorgeous, but if its closet to 1 carat the emerald might look small to you. We had to size up 1/2 carat from what I originally wanted to get the look we wanted.
Oh and as swanky said, emeralds do not sparkle, they "flash" and while they look shiny and still catch the light...it is totally different from the more faceted stones. But with the pave halo you will still get some sparkle no matter the shape!