I use both all the time (a LOT) and have no problems! I'm not sure which is better for A6, but really I can't tell the difference. If there are some 5 sided faces sometimes the engine will crash as it loads, but usually 3 and 4 sides work fine. Probably someone here who is more technical could point out one is better than the other, but my 3-4 mishmash works without a hitch. Hope that helps.

Usually if I have a problem with a 5 sided or mysterious problem face I just triangulate the face and suddenly it works.