Hey Oscar.
If you're interested in the Vanguard in 300Wby, I would have to say go for it! I have one of the Sub-MOA variants they put out a few years ago, they still list it on their website at RRP of USD999.00; I would personally would only buy one if you're going to get the sub-MOA. These are rifles taken from standard production, however a perfect combination of barrel, action, machining tolerance and workmanship sometimes result in a very accurate factory rifle. I guess Weatherby are taking advantage of good QC.
Weatherby Vanguard Sub-MOA
You'll lose a good 100fps with the Vanguard's 24" barrel as opposed to the standard 26", but nothing at the other end can tell the difference. I load mine exclusively with a 180gr Woodleigh Protected Point at 2950fps and 5 shot groups average 0.75".
The recoil out of this rifle is easy to handle as with the standard recoil pad the rifle really does bounce and if you have a good gunsmith, the trigger is not bad and can be adjusted on the light side with 100% reliability (in my rifle after 3 years and 500 rounds).
My rifle wears a Leupold 4.5-14x56 VXL which sits very low around the barrel and with this scope I have shot pigs in full moonlight without a light on stubble paddocks.
As far as the calibre goes, you're obviously looking to shoot at some distance if you're taking a .300 over a .308Win... My best one shot kill was a fallow stag at 515 metres. Carry a trajectory chart taped to the forearm and a range-finder and you're in business! I've attached the ballistics charts for my pet loads.
In Africa I have taken maybe 30 species with this calibre; all shapes and sizes. Mountain Zebra at 250 yards, Sable at 275 yards with full length penetration, Tsessebe at 150 yards, Jackal at 300 yards, Caracal at 30 yards!
I would feel comfortable using the rifle on most game; I prefer something a bit "fatter" on Eland and Buffalo - they just look big! You also have minimum calibre regulations for some of the big stuff! I personally would not use it on the heavyweights.
Outstanding choice. Look after your barrel, get a good scope, and take a solid rest, 'cause 300 yards is a long way even for an accurate rifle!