Same gears in each truck? Same size tires?
If so then the TBI will be very close to the vortec. Now stock for stock the vortec will be a bit higher, but for about $100 on the TBI engine you can pick up some MPG to make up that difference, where as with the vortec you would need to spend more, parts are more, the parts that do go bad are more, and the push button 4x4 is more prone to go out then the floor shift.
IMO I would buy the TBI truck, my 95 ECSB with just some longtubes and single 3" exhaust and a TB spacer was pulling down 17 MPG Hwy with 3.73's gears and 265/75/16 AT's on stock aluminum wheels. TBI is easy to work on, parts are cheap and easy to come by, very reliable, and easy and cheap to mod for some decent gains.