I think the key is what Jeff touched on, do you want to be able to resaw? I think you would need at least a 14" to resaw well. I think you always buy the best you can afford and you won't be disappointed. I have a 10" Ryobi bandsaw and it works good for me. All I do is cut off pieces for scrolling or rough outline a pattern.
Jimbo makes a great point, cheap is (can be) dangerous.
Barry