I've got a lot of experience with Muela because for a long time Spanish brands where pretty much the only ones you could get at stores in Argentina (Muela, Aitor, and so on).
Which model are you looking at? "olivo" and "asta" are just handle materials (olive wood and horn). Since you're looking at hunting folders, I guess you mean the BX-8 series (440 blades most likely 440A, nickel silver bolsters and olive, stag or ram's horn handles). Muela has decent fit and finish, some of the materials they use on their cheaper fixed blades are not very good (zamack guards and pommels, and stuff like that) and they tend to settle for rather pedestrian stainless steels even in some of their more expensive knives (sometimes they don't even bother listing the type of steel used).
I got rid of all my Muelas except for a folder pretty similar to the ones you're looking at, with olive wood handles and no bolsters. It's quite well made and has held up fine over the years. However, Benchmade is a step or two up in quality and blade steels are much better. The Hunt series has S30V blades, much better than anything offered by Muela. Two of the models have Axis locks, again much better than anything Muela can offer.