[chinds85]

I think when keeping an authentic borscht in mind, a touch of vinegar would be a better thing to add for sour taste. I'm not sure if many borscht recipes call for lemon juice (that would be more towards the mediterranean). If you arent going for authentic, I would imagine that either choice would create an equally delicious outcome, though I do not have very much experience with this slavic soup. Good luck and perhaps someone else will be able to give you much better information.