If you can afford it, buy the Deardorff. I personally don't think the Wisner's are built nearly as well nor as precise as the Deardorf. If you end up paying $400 more or so, believe me in a few years you'll have long forgotten about that extra few dollars. You can also wait a little for a used Canham to show up on eBay. I've owned one for over 15 years now and it has never failed me. Haven't tried a Wehman, but I did own a KMV for several years and I really liked it except for the short (28") of bellows draw. The Canham has 36" and that makes a big difference.
That's a little better than the KMV, but when you reach the limit of the bellows, it restricts your camera movements. I have run into this problem with the KMV (but rarely). I've only seen pictures of the Wehman but it looks like a nice camera built with usability and functionality as the primary goals.
I've owned two Deardorffs, they're great cameras. I haven't kept up with their current pricing but based on what I paid for my second one which was absolutely mint, I think the winning bid of $2500 was very high. I think I paid $1800 on ebay. But that was a couple years ago, maybe the going price has increased since then. The Expedition would be very tempting though, especially if it weighs significantly less than the Deardorff's 12 lbs and especially if ended up at say $2000 to $2500. I'd have to investigate the specs of the Wisner, do some research, etc. before I could say which I'd buy but assuming the Wisner doesn't get beyond $2500 I'd probably go for it.