I have the standard and got what i thought would be a good upgrade to the max version, i should have saved my money as there's not much of a difference.
Go for the MAX , the design is different and therefore you do not need to remove the stock shock cover when fitting, neither do you have to faff around with shims to get the clearence correct between the nudsling and shock.
They do a combo pack if your thinking of a fenda extenda for the front mudguard as well. http://www.nippynormans.com/product...ant-r1200gsr1200-adv-all-years-mam-combo12mgs
I had the standard MudSling fitted which I replaced with the Max version after a crack appeared and progressively got worse. The Max is an improvement over the standard MudSling buy keeping more crud off and also looks and fits better.
The Avant fender extender is also a big improvement and can be bought as a pair and well worth the extra £20