I shoot 3under. But wish I didn't. Some bows never shoot well 3 under. And most bows out there used are tillered for split. 3under is good for gap shooting up to 20-30 yards however.

Split is putting equal force behind the arrow. Where with 3 under, your release can be more sensitive depending on how that ring finger is positioned at release. Thats why some even shoot 2 finger split.