I'm looking for a light x-c bike but seem to be right in between sizes. At 5'8" and a 30" inseam I fall right between a 16 and an 18 inch frame. My riding style is a little upright and I'm not real keen on a streched out riding feel but do ride aggressively and fast. In general is it better to ride a little smaller or bigger frame set. I'm looking for a light hard tail race type bike and won't be using it for big drops..just tight, fast, rough, up and down single track. I do ride a medium size FS bike that is just a bit big.
Any help or suggestions much appreciated! 16 or 18?