I've used 150mm a lot, but for the past two years I've been using a Nikkor-W 180mm f5.6. I prefer the slightly longer focal lengths. As Doramus Scudder points out above, though, the slightly shorter focal lengths (135, 150) allow you leave a little more "air" in the picture to facilitate cropping. After all, when using the large formats and doing darkroom work, the large areas of a 4x5 allow significant cropping with insignificant loss of quality in the final print.

My game plan is usually to frame exactly if I have done the shot before (I like to revisit sites and retake pictures under different conditions) so I use the 180. But if I am shooting something for the first time I'll usually leave air so then go to my 135 Schneider or my 150 Fuj.

So I suggest you start off with the 150, and when you feel your way around, go the direction in which your shooting demands. You'll end up with two lenses, one allowing more air. Not a bad way to do it.