If you're looking for portability, the CoaguChek XS is not a bad choice. It's relatively compact, the strips don't take up much space (they usually come in a 'tube' with a cap on it, and if it's anything like mine, it even comes with a travel case.
For myself, although I've used the XS, I personally prefer the Coag-Sense. It's bigger than the XS. The travel case, with strips, transfer tubes and lancets is larger, but it can also travel well. I haven't done much traveling recently, so the issue of portability isn't a big one for me.
What I like about the Coag-Sense is that it seems to report INRs slightly lower than the lab results, although the actual calculated prothrombin time sometimes matches the lab. In my experience with the XS, results are usually slightly higher than the lab. Both seem to meet the 30% range of error guidelines that have been established for INR testing. Personally, if my meter gave me a value of 2.2, I'd feel comfortable knowing that it was probably AT LEAST 2.2, and possibly higher if I had a blood draw; a meter that gives me a 2.2 and is consistently higher than the lab would have me a bit concerned about how low a lab result REALLY was.
Both are good meters. The XS is probably a bit easier to use than the Coag-Sense (because all you have to do is put a drop of blood on the strip, or touch the side of the strip and let the strip draw the blood in).