before QV, i tried LFC labs and spectro. THey were good, but to me, QV is a great product. All my gear comes from them, their cheap, good quality, if something aint broke, don't fix it.
denkall has a slightly better rep and costs more. Quality is very similar. QV did initially have some problems with their high mg injects, too much solvent... though the same can be said of the t400 by denkall.
really about the same-- right now... that could change as quality and consistancy have not been strong points of mexico--