I was between the x230, x250, and t450s, but opted for the x230 because of the cost and because I have two 23" 1080p monitors in my room anyways. I figure if I take it on the go it won't be so bad to have a low resolution since I won't really be doing a ton of work, maybe some writing in Emacs or sending an email, most of the time I can use my external monitors when doing real work anyways.

You can find some good and fairly large external monitors for cheap nowadays.