I vote for small, quick and responsive instead of large and sluggish. If the top tube is a tad too short I just get a longer stem, like dolface said. But there's a thin line between small and too small and that's what sometimes can be a bit tricky. I don't like it when the rider looks like he's going to crush the bike because of his bigger size. It's all about harmony between the rider and his bike. A little extra room for your friend below is never a bad thing either.