The '88 Premis would be much more of a performance bike, with better frame tubing, more refined components, 700c rims, and at least several pounds lighter than the '78 le tour. The le tour will have high-ten frame tubing, straight-walled steel 27" rims, etc. etc. Le tours, Travelers, etc. from that era are nice riding bikes, great for casual road riding or commuting around town, but they're not a close comparison to a late '80's Schwinn intended for performance road riding. So the bottom line is the price, the type of riding you want to do, and your personal preferences-