The Mule is easy to add attachments to, but needs to slide all the way down the rails to be removed. It's also all aluminum.
IMO the Delta T3 is a much beefier and simpler system for the same price....best bang for the buck going.
The Vega is a really nice fence, with the best microadjustment I've seen....pretty easy to install too, but obviously costs more.
The Incra is in a league of it's own for precision and repeatibility, if you need that sort of precision....it takes up more space to the right than other systems.