Well rounded (and the other)
Well rounded is like a resilient ball, rolling about, likely to be pleasing to most, and built to last.
The opposite?
Sharp.
Sharp is often what we want. We don't want a surgeon or an accountant or even a tour guide to be well rounded. We have a lot of choices, and it's unlikely we're looking for a utility player.
Well rounded gives you plenty of opportunities to shore up mediocrity with multiple options. Sharp is more frightening, because it's this or nothing.
Either can work, but it's very difficult to be both.