Skog,
I'll start off by admitting up-front that I have never owned a Weatherby Mark V or Vanguard. I should also say that I probably never will own one, as both utilize push-feed actions, which aren't my cup o' joe (I'm biased toward the controlled-feed actions like the M-98 Mausers, M-70 Winchesters, '03 Springfields, and so on) and I'm not overly enthused about the "Weatherby Styling", favoring the "classic" kind of stock style with a rounded fore-end and a high, straight comb on the butt stock.
That said, I've shot several of both, as I have hunted with folks who swear by them. All of them that I've fired were more than adequately precise to take big game animals out to any reasonable range that such creatures should be shot at.
The differences are in the locking lug arrangement, as a prior poster noted. The Mark V is thought to be the "stronger" of the two. It also has a shorter bolt lift -something like 65 or 70 degrees versus the full 90 degree lift of the Vangard with it's dual, horizonally-opposed locking lugs. The Mark V's I fired seemed to have better triggers than the Vangards that I fired did. Currently, the Mark V's are produced in the U.S.A. by a defense contractor that makes really big firearms for the military -machine guns, artilery pieces, and the like.
As to the question of whether or not either is "worth the money", that's one that only you can really answer. I wouldn't spend my own jack on one, but not because they aren't fine, well-made rifles. They just aren't my idea of a fine rifle. But then the A-Bolt, Remington 700, Ruger M-77, Tikka, Sako, and so on aren't, either.
The .270 Weatherby is a good cartridge, but it isn't a particularly efficient one and I doubt whether any animal shot with one would die any quicker than it would if shot with a .270 Winchester. If you're committed to the .277 bore size, you might want to think about how good the .270 Winchester is and how little practical advantage there is to be gained by going to the longer, fatter case of the Weatherby round. The current .270 WSM or "short magnum" is argueably a better cartridge design than the Weatherby is because it is more effecient.
The problem with .277 bullets is, well, that they are .277 bullets, and you don't have as many choices as you do with .308 bullets. I'll put it to you like this: You can't shoot 180 grain to 220 grain bullets out of a rifle with a .277 bore, but you can do so out of a rifle with a .308 bore.
That's not a huge deal with carabou, as I don't think they're as tough to put down as elk or Alaskan moose are. I would suspect that a .270 Whatever would probably get the job done, but I know that a .30-'06 will.
As boring as this sounds, if carabou hunting is on your horizion, the old .30-'06 is tough to beat.
Oh, and before I go, I am compelled to take exception to the idea that a Mark V Weatherby is a "wallhanger". I've known over a dozen people who take their hunting seriously and wouldn't dream of hunting with anything else but a Mark V in some flavor of Weatherby Magnum chambering. These folks hunt with their shiny blued steel and walnut Mark V's in weather fair and foul, and in far more exotic locals than I hunt in.
-JP
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