The big difference is the ruggedness. If you look at the Mk4, Badger, IOR, you will notice the rings and bases are much larger, bulkier, and have larger (and some times more) mounting screws (at least on the rings). All of this means you can use (abuse) your rifle a bit more and have a better chance of everything holding zero.
With the standard leupold bases, I don't think the standard "windage" adjustable screw on the back that holds the rear ring on is nearly as robust as a standard weaver type (especially a heavier weaver type). The dual dovetail design I feel is better. Now, if you plan to be gentle with your rifle and use it mainly for range shooting, then the std units will serve you well. If you plan to use your rifle in field as a tactical rifle, then it might be wise go with a bit more robust system.
I kind of like the leupold std LR bases (for the money) but I wish they would do a double dove tail in LR, as like I said, I don't like the std rear ring mount.
MEL