If you decide on a vanguard, you'll be pleased. If you go with the Mark V you will see it has a better stock, receiver, barrel, trigger, .99" or less guarantee at 100 yards. etc......
You are concerned about the extra 2 " barrel length. You might lose 50-75 fps with a 24". Then again, you might not. It depends on barrel.
I would recommend the Vanguard in the .300 wby instead of the 300 win mag. If you hunt elk or moose, the .300 Wby with 210gr. bullet traveling at 3000 fps the rifle trajectory will be flat, maintain energy down range and bullet drop out to 400yards will not be a factor.
I have both a 300 win mag and Wby and if I am hunting anything bigger than a whitetail deer and/or out west where long shots are the norm, I seem to gravitate towards the Weatherby.
If the Vanguard you choose is costing you $800, then I would opt for a Mark V in weatherguard 26" barrel and 9 lug Mark V superb magnum action and the LXX trigger is the best all for about $1300. It is the most economical way to own a Mark V. It has all the important components that makes the Mark V the best rifle out there.
If you want to keep your costs down go with a vanguard. The Wby Vanguard is still a better built rifle than most $1200 name brand rifles. The Weatherby mark V, in my opinion, is a factory gun shop custom rifle for 50% less than a known name custom rifle would cost you. I have owned Weatherby rifles since 1971. They are quality through on through.
Of course, my opinion is just that, an opinion.