The El Bolso bag is a open-at-the-top bag that does not enclosed the bike with zippers or other such closures. The Nasbar bag appears to have zippers to close it up. Both seem to do it's job as they use similar type synthetic fabric, and tote the bike around when folded up.

As for price, I use US retail prices as is my habit. For example, Performance Bicycles offers the El Bolso for $64.99. Nasbar offers it's version at 39.99. So there is a price difference of about 25 or so dollars (excluding tax, shipping & handling fees). Which one would I buy? It depends on what you want it for. If you want to hide the bike completely from prying critical eyes, transport it, or something similar, a zippered bag is the best choice (providing you know your own bike's exact size). If you want to cover it up with ease and very quickly for home storage, taking it aboard buses/trains/private auto for commuting purposes, or the like the El Bolso is the one to choose. And you don't have to worry about it fitting for the most part as it claims to fit a wide range of wheel sizes.

Which bag do I actually use with my own folding bikes. None of the above. I either buy my bags at a discount store or make it myself.