The bottom line is that it is better if the bike fits properly. A "good deal" is not so good if the bike does not fit you properly. As for purchasing and riding a bike that is too tall or too small, that is a personal preference. If it is really necessary to pick one, I would not be surprised if it is about 50/50 on whether cyclists prefer too big or too small. I personally would prefer a bit too big, and, in fact, have a bike like that. I use a shorter stem, lower the saddle and move it forward a bit. I am quite comfortable on it. However, I do not ride it that much any longer as I have bikes that actually fit, and I prefer them.