I think simple always wins, and that is Upvotes + Downvotes. It gives you the size of both sides of the coin, while it also allows me to kinda see "woah, this post is generating lots of engagement", whereas score + % may show a 2 + 50% and I don't really know what that means.
2 + 50% means that 51 + n people upvoted and 50 + n people downvoted, where n is a natural number. Making the % (x): 50% < x < 50.50%, where x is rounded down to 50%.
A smartass and wrong! You obviously messed up thinking OP's initial upvote wouldn't count towards the percentage. The correct formula is n + 2 upvotes for n downvotes, which makes 0.5 < (n+2) / (2n + 2) < 0.505, solve for the smallest possible n₀ = 100, giving us 102 + n upvotes and 100 + n downotes