Which would be best all-around choice, for tows of 400 miles or less, and to live with on a day to day basis, and to not break down with expensive engine or tranny problems?
1997 Suburban 2500 with 7.4L and tow package, 130k miles
2003 Chevy Express 3500 15 passenger with 6.0L and tow package, 215k miles
both going for about $4000.
Neither, unless you plan to completely overhaul the chassis and powertrain. Regular 400 mile towing plus daily driving is not a 5 mi trip to the boat ramp that you want to chance with well-abused ball joints, tie rods, and valvesprings. If the ones you're eyeballing have a big hefty hitch with plenty of scratches and rust, I'd be even more wary. 5w hitch? Forget it. 3/4-tons aren't typically used to tow Sea-Doos.
A while back I thought about getting an older tow vehicle like that and building it back up. For example, I remember building a "wish list" for a $1500 '94 Sub involving a chassis overhaul and a GW 350/TCI 700r4, but decided against it after I realistically calculated all the costs involved.
After lots and lots of looking and calculating I've concluded that something 5-7 years old with <100k miles plus a good aftermarket warranty (i.e. warrantydirect.com) is the best bang for the buck. I already have one rotting project car and I don't need another.
Plus, there's the size and MPG factor for what you drive on a daily basis. If you don't have to tow more than 5000# and live/drive in a space-challenged urban area, there are plenty of compact/mid-size trucks that can do the trick with a few key mods and the use of common sense. Going from big trucks to a small one on a daily basis made a world of difference in ease of driveability, for me anyway.
As far as big GMs go, the '99 (or '02+?) HD trucks come standard with the 6.0 (decent power), have trans temp gauges, and even the stripped work trucks often come with cruise control. Some even come with some sort of plug-and-play TBC connection. I remember last year seeing an out-of-work construction contractor fleecing their their superintendent trucks, selling 2500HD reg-cab 60,000-mile late-model Sierras with hitches, toolboxes, TBC plug and play, and cruise control for like $5,000 or something.
The vans don't have the TT gauges or the TBC port, nor the easy visibility of a truck, but you can't beat a cargo van for space and ease of access, especially on race day in the paddock. After having to drive one ('06 2500 Express Cargo 4.8) every day for 2 months and using one for work off and on ('90s E250 4.9) I wouldn't want one as a DD. If I had $/space for a dedicated tow vehicle it'd be a full-size van, no question. Considering I want a minimalist trailer, there's nothing else that will swallow gear/tools/air tanks/tires/luggage/etc. like a cargo van.