The first Honda with IRS was the 2003 650 Rincon. Honda has a die hard thing about not letting go of the old SRA with a drum brake.
Even their expensive Rubicon and Foreman are still using it in 2014.
The Rancher now has a IRS version and the 680 Rincon are the only IRS Hondas.

The only Limited slip IRS I heard of was the Polaris with a "turf mode" for manicured lawns but it could also be fully locked when need be.

Not sure how much more the IRS Rancher is over the SRA version.

Another advantage of SRA over IRS is it does not have 4 rubber CV boots to worry about ripping and changing which is nice.