I'll open my "big Northeast mouth"... .
I have seen literally hundreds of 4x4 duallies towing fivers.....
A dually tows better than a SRW truck..... no doubt about it.
Duallies are more expensive through the tolls.....
Duallies require you to buy 2 more tires when you need 'em.....
Duallies are 6" wider than a Hummer
Um, that's about it..... there are only a few downsides IMHO..... and they're not even that major at all..... Heck, I'd buy one!
If it were me, I'd look for a '98. 4 - 12-valve, 2500, 4x4, quad cab, short bed, 5 speed, 4. 10's, AC, cruise... you know the rest.
After driving an '02 - H. O. ISB, 2500, 4x4, quad cab, long bed, 6 speed, 4. 10's..... with DDII's and an EZ box... . it's a sweet combo..... extremely smooth ride, plenty of get-up-and-go... and very comfy on the long hauls... .
Around here you can buy one heck of a good truck for $21k if you look for 'em.....
Matt