Given the choice I'd probably go for four limbs with opposable thumbs on all and a slightly-reduced ability to walk efficiently on just two of them than be fully or mostly quadrupedal; the latter might be faster and more efficient but there aren't many exclusive quadrupeds with non-functional digits with the ability to cogitate abstractly or the ability to design or use tools any more complex than those can be made or picked up in the teeth or trunk. In a way it's a shame that somewhere down the line since Australopithecus that our myosin degraded, reducing our weight-for-weight muscular strength compared with our co-descendant primates - stronger and faster, they get along fine switching between two and (though far more easily) four legs on the ground yet also maintain the handy abilities of arboreal locomotion such as brachiation and have opposable thumbs on all four limbs though they lack the fine, precise motor control of the fingers that humans have evolved; whilst relatively inefficient muscles could be considered a setback there is a school of thought which suspects that the lighter skeleton permitted by a weaker musculature allowed for various structural adjustments to our heads and bodies and vocal apparatus which went hand-in-hand with the development of our brains. Hmmm.
I did get a nice picture whilst bicycling about this morning and lots more (mostly of trees) when walking about in the afternoon but I've only assignmented one picture so far so felt I ought to do something. This came to mind.