What Steve said, he gots it. I also prefer solid axle with differential.
Note: You can get a smoother ride on a Tri Glide with just a rear shock change if you think the stock is to rough. There is also a lift kit that can help as well.

 

i rode both, i much preferred the ride of the irs. took my 15 limited to a local indy who's also a road smith dealer and did the conversion, its also got a 10 inch longer wheel base, the harley axel is directly beneath the better halfs *** and does not ride as good.the road smith got me running boards racked front end elc reverse and matched perfectly 2 tone paint and progressive shocks, heavy duty sway bar(wife and myself or not small) installed for 15.000$ +22,500 for the end of year limited. for about the same money i gain the limited options but will likely loose any harley warentie. skipped optional 3 gallon tank and wheels and bumper.

 

A regular Harley Trike with a lift kit is the way to go.

 

The only real problem with a Roadsmith is if you have problems on the road it might be hard to find warranty shops. Maybe Roadsmith has an agreement with shops, maybe not.
I don't know what Harley's warranty on the front end is anymore. They used to have no problem as long as it was Harley.
You will gain rideability with the longer wheelbase, but loose some turn radius. Also you gain some weight with that extra length. Fuel millage might suffer a bit.
I would guess a nice SE120 might be in need.

 

Yup, all the HD factory TriGlides have solid rear axels with a differential. Mine corners like it is on rails. IMHO, with the narrow rearvend, I can't imagine the weight, cost, complexity, reliability of a true IRS is justified.

 

I had a DFT kit on a Sportster with IRS a few years. It didn't handle any better than my 15 TG. By the time most kits are installed you lose the cost advantage. The TG also gives for a full warranty anywhere you go.

 

The 14" Trike Series Shocks solve the "issue" of the solid axle on the HD Trikes.

The TSS will give the HD Trikes a ride quality approaching/surpassing IRS for a fraction of the price, but maintain all the handling benefits of the solid axle.

Check out his Rear Suspension Report.

 

All rear wheel drive cars have differentials.

Non IRS cars have solid outer axle tubes that are welded to the differential, IRS cars have outer axle tubes that pivot.

 

bingo !