Does the Portland have room and mounts for full fenders and a rack? Look for clearance and mounts for full fenders and racks. If you have plans for anything but good pavement, you may want to look for a bike with clearance for fatter tires. Fatter tires help protect the rims from damage from potholes and rough roads and make for a smoother ride. They may roll a tad slower, but you could put skinnies on for a fast weekend ride.

Unless you only plan on commuting on warm, dry days, full fenders are a necessity. They will keep more mud and sand off of you and your drive train components, greatly extending component life.

Given the choice between the X-check and LHT, I would take the X-check for your purposes. The LHT is a tad heavier and has a tad more sluggish geometry, which is nice for heavy touring but not so much if you don't need that extra capacity.

Disc brakes are very nice indeed, but I would put full fenders, easy rack mounting, and maybe tire clearance above them for your purposes, especially since you don't have much in the way of hills.

Have you test ridden any of them yet?