m720v or m620v

[JRas]

Trying to figure out which light I should go with for my carbine. Which would you go with and why?

m270v
http://www.tactical-life.com/online/wp-content/uploads/2011/04/02-m720v-tn.jpg

or

m620v
http://external.ak.fbcdn.net/safe_image.php?d=AQCSDD1ONP5to0gb&url=http%3A%2F%2Fecx.images-amazon.com%2Fimages%2FI%2F41RkbkAuWfL.jpg