Looking at Bushmasters and DPMS catalogs.
I think I would someday like to get a shorty AR and I am wondering which I would like the standard shorty model or the Dissipator which has the standard handguards and longer sight radius. What are the strengths and weaknesses of these rifles?

for me it was the sight radius, the longer the better and i went with the dissipator. if you wanna scope it, it doesnt matter.

I chose the Dissipator for the same reason. It seems like the best of both worlds. The compactness of the carbine, with the inherent long-range accuracy of the longer sight radius. More versatility. I've wondered if the shorter radius of the Shorty or M4 would make for faster sight alignment at close range, though. If I were to buy another carbine length upper, I think I'd choose the one Bushmaster calls the "Patrolmen's Carbine". It's an M4 profile barrel, but is stretched to 16" instead of 14 1/2", and has no blast enhancer (AKA muzzle brake).

I bought a Dissipator for the same reason, if you get the same length but a longer sight radius, why not? Mine shoots great! VERY Accurate (it is an Hbar, so, a little heavy for a 16 inch) I love it. You just have to weight the advantages

To make life even more complicated, Armalite (and possibly some others) have an AR-15 carbine with a “mid-length” handguard, which I really like.

The traditional shorty handguard is too short, esp. if you decide to add a tripod.

The Dissipater is no doubt the smart way to go; it’s just that I find it so ugly!!  (I don’t have to be smart if I don’t want to!)