I think both - a symmetrical horse would be better than one leg that is not balanced with the rest of the body.
I had a horse that toed out in front - symmetrically. That horse was SOUND - wholly heck he did a TON of jumping, eventing to prelim, hunters, jumpers, fox hunting you name it for 7 years - then went on to the next young girl and spent an additional 6 years showing on the A circuit in the hunters - then onto the next girl and even more jumping - that horse was worked hard from the time that he was 6 till 22 that I am aware of - and stayed sound.