Why not stitch panoramas in photoshop or PTGui?
I do do this, I use PTGui. Sometimes, when there are nearground elements, it introduces wierd persepective distortion, what is right in front of you is out of shape with what is in the corners. Your third image may possibly show this, but I wasn't there, so not sure. If the info in the image are farther away, then this effect goes to zero.
Also, with stitching if there is wind or things are moving sometimes it can't work. In my gallery on photo.net, the wide yosemite image is stitched with PTGui (http://photo.net/photodb/photo?photo_id=6756438
). I also have Linhof 617 images - I far prefer what happens when it all comes in on one image. It is so much better to get everything you can get right in the image at once if possible.
Okay - ignoring stitching now, there is another issue. For wide angle lenses: Small Format SLR < Small Format Rangefinder < Medium Format < Large Format (i.e., Schneider Digitar). If you look at the MTF and distortion values you'll see that at 90+ degrees field of view the Schneider and Rodenstock wide's are really king, with Medium Format wide's coming next. If I understand correctly, the Hasselblad/Zeiss Distagon T*40 CF IFE, the new Mamiya 28mm lense, the Mmaiya 7II 43mm, the Hassy 28mm for their digi system, these are all tons better than the wides available in 35mm, film or digital. The Zeiss/Contax/Leica rangefinder lenses come in next - and if someone wanted to argue that they are equal/better than the MF lenses, I can see that perspective. I don't think anyone disputes that the Schneider/Rodenstock wides, especially the new digi wide's, are by far best of breed. Compare MTFs and distortion curves!!! Almost no comparison on distortion.
You'll note there is a bit of resurgence in film... Film companies are releasing new films, and sales are going up. Not to turn this into film vs digital, but in particular because the rays of light come in at a stark angle for wide angle film is still king. The sensors don't like it coming in at those intense angles. Very modern wide angle lenses designed for digital, like the new Mamiya or Hasselblad 28mm try very hard to minimize that as a design goal, but it is hard to get around.
Note, however, there doesn't have to be such competition!!! For example, if you get a Zeiss Ikon WA with single superwide lense as mentioned above, or with the Tri-Elmar, then shoot film for a year. Drum scan the images you really like, and find a lab that scans with a Hasselblad Flextight for a less costly but still great scan for the rest that you still want to blow up. After a year or two, you can get a Leica M8.2. Also, many of the 6X7 or 6X9 film cameras support digital as well. Start with film and then perhaps rent a digital back and see if you like it.
Cambo Wide DS and 6X9. Schneider 47 lense. That gets you around 102 degrees (width! diagonal degrees would be even more) angle of view. (How do you get 102 degrees of view on digital SLR? Unless you do fisheye/alter in computer or stitch, I don't think you can) Then wait a year or two, (or 6 months ) and then rent a digital back for a weekend. Some of them are coming down to the 10k or 7k range, so its not impossible to buy one, and three years from now as prices keep coming down, it might be 5k. You'd want to add a Schneider 24 or 28 or 34 or something as your back will be smaller so to get very wide angle you pretty much have to get the widest angle lenses available.
Another really simple example is to get a Mamiya 645afdIII. You can add the Mamiya digital back after a few years if you want. So in the short term you get an amazing camera, and with that 28mm lense, an *amazing* wide angle lense. Then go digital if you shoot tons of images or just like the digital workflow in future.
You asked what some of the 6X7 cameras are, there are Mamiya RZ, Mamiya 7II, there are others, but the MF industry is sort of standardizing on Mamiya and Hasselblad who are more focused on 6X45. Historically the Pentax 6X7 was a great camera, for example. And then the tech cameras, which can get very expensive can all do 6X7 and 6X9, but one that isn't so expensive is the Alpa TC. And the Cambos. Other tech cameras are Sinar ArTec, Linhof Techno, etc. They can get extremely expensive, though. Horseman makes some great less-expensive tech cameras. Their site seems down right now so can't get specific numbers, I know their 6X12 is quite popular.
The abilty on the Alpa TC, for example, to throw on a digital back or a film back is great. And with the Leica 8.2 there is a similar option with the Zeiss and Leica lenses - the Zeiss Icon WA is *so cheap* compared to high-end digital SLR, start with that shoot film for a year or two, and then go Leica.
Oh - if you stitch don't use wide angle lenses. They don't stitch well, especially if from a digital SLR because the high distortion inherent in those lenses makes them harder to join well. There is some computer-based distortion correction and that can help but I've found it can add distortion to some objects depending on what is in the image. When I stitch I use a 35mm (equivalent in 35mm, its really 55mm) lense oriented in portrait as that lense in the Mamiya 645afd line has almost no distortion. If I used the 28mm equivalent or 21mm equivalent, the images would be harder to join. By going less wide angle, shoot in portrait, and take more images, they come together on the computer better.
Have fun searching!