I have to go with Ren on this. If you like the sound of a steel string acoustic then I would recommend going in that direction. A huge part of success in learning has to do with keeping your interest. If you're not crazy with the sound of nylon, you'll grow bored playing it.

Like Ren said, it does not take much time to build up the callouses. Once you have them, they are a badge of honor! :)

In all seriousness, buy the one you enjoy playing and listening too. I think you'll be much happier in the end.