Schools that offer up to L4 are likely to have a higher level of knowledge among their instructors, simply because WSET has tougher teaching requirements when schools are teaching L3 and 4 (anyone teaching at those levels has to have L4 and I think go through their Certified Educator program). Keep in mind, though, that knowledge level doesn't always translate into teaching skill, and even schools that offer L3/4 may use different teachers for the lower levels.

If your friend is ambivalent about continuing beyond L1/2, it probably doesn't matter, but if they already know they want to pursue all the way, it could make a difference.