Forget about single-point unless you're a mall ninja wanting to rack yourself walking about hands-free. That leaves 2 or 3 point. The KISS principle leans toward the 2-point sling, although I do have several 3-point that I do really like.
My main obsession, with regard to slings, has become the QD swivel. Forward or rear on the handguard (built in to the front of my LE6940) and plenty of butt stocks have QD attachment points. QD on the single-point position is nice too, except for said notorious racking of the jewels when utilized.
There are some really expensive slings out there but a $9.99 Blackhawk! with 2 QD sling swivels is hard to beat.