If it will be an ornamental, then chose the one that is aesthetically pleasing. I imagine that would be the runt.

If its going to be indoors, pick the shorter one for sure. You're going to have trouble with it getting too tall eventually (years from now) so picking the smaller one to start off with should serve your purposes better, seed grown trees are tall but can be managed with pruning, unfortunately if you ever want flowers or fruit you will have to let it get really big (a high leaf count) to tell the tree its mature enough to reproduce and if you prune it back to much it will likely never happen. but if you just want a leafy tree indoors you should be able to do any pruning you will need to keep it off the ceiling.

Can't you keep both for a while...see which ones develops best with a bit more time?