Found this thread after searching a bit...
Problem that wasn't mentioned, is the "squat" of IRS with one driver on the ATV.
My 200 lb buddy was on his brother's Rincon 680 this weekend and it sags even w/ only 200 lbs. Looked like at least 1.5 or 2" ground clearance was lost. Earlier that day, two 215 lb guys were on it, squated almost where the axles were level w/ each other!
IRS may still be smoother and better for deep mud, but after riding a 300 fourtrax 4x4 and going everwhere he could with no problems. I'll be getting SRA. No matter how much weight is on the back, it won't sag, unless tires give a little.
Something else I thought of, is the "ground clearance is based on the lowest point on the chasis. Other than rocks and such, if you are going over rice levy's or in deep ruts, hit them straight on rather than stradleing them and should be same as any IRS machine right? Just a thought. Thanks

 

My first quad was an IRS. My second was an SRA that I rode on the same trails and was constantly hitting rocks and things that I used to sail over without touching. It would clear a stump about half as tall as the other one. It high-centered and got stuck in the mud and rutted out trails too. The next year I traded it in for another IRS and every one since then has been an IRS. I'll never buy another SRA as long as I live. They work okay for some people in some places, but they don't work for me where I ride.

 

I ended up buying a SRA Foreman 500 w/ 26" tires. Measured Ground Clearance tonight, and it's just shy of 9". I'm running swamplite tires. My friends Rincon (irs) has appx 12" w/ the tires he has, but w/ two people on it, he looses at least 2", maybe more. I drove a Rancher 420 IRS and didn't like the "body roll" at all. The SRA seemed much more stable and will be more fun to slide around on the trail with. Hope this helps someone else w/ the age old debate of IRS or SRA!

 

Had them both. Straight axle is great for work, IRS is great for comfort and Ground clearance. 70% wood hauling, you made a good choice with the SRA, but if it was 70% trail riding over rough trials your butt and back would disagree at the end of the day.

I power side with my IRS machine all the time,"power" more than rear suspension type determines what ATV can do a power slide the best. Some IRS ATVs do not put a torsion bar on at all, which also makes a big deference.