It's not just size and toughness.
The Vaqs use the Ruger "New Model" action, which has a transfer bar safety. More importantly, the loading drill is completely different from an SAA or true clone like most of the Italians, the USFAs and the like.
On a true SAA pattern, you reload by:
1) Half-cock the hammer;
2) Open the loading gate;
3) At this point the cylinder bores will line up with the loading gate on each "click" as you spin the cylinders.
4) Empty it, then load one, skip one, load four, lower the hammer. That leaves the hammer down on the empty sixth cylinder bore.
You load it "five up" only because there is NO safety on a true SAA pattern gun.
On a Ruger, you leave the hammer down, open the loading gate, have at it - and go ahead and load six if you want, it won't go bang if you drop it or jar the hammer.
Problems with the Ruger: the cylinder bores click when the bores are NOT aligned with the loading gate, and if you spin too far you have to go all the way 'round again to get that one. Which is why Power Custom sells tons of $35 freewheel conversion pawls (cylinder then spins both ways) or this same "freewheel conversion" is done by many gunsmiths, such as Linebaugh, Bowen, Stroh, etc.
On the Ruger, it's also trickier to set up the gun five-up with the empty under the hammer. But with the automatic safety, you don't need to, right? You do at a SASS/CAS match - the rules permit five-up carry ONLY - so as not to put real SAAs at a disadvantage over the Rugers, Bounty Hunters, Stampedes and other such "old looking, newer innards" guns.
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The USAF Rodeo (and their cosmetically higher-end cousins) were designed from the ground up as CAS/SASS "ultimates". The sights are as good as are allowed in the SAA's fixed-sight class, the loading/operating drill is identical to a real SAA, the quality is first rate, the size and handling is very close to the SAA except that the cylinder is a fraction oversize to give a bit of protection to handloaders without going all the way to Ruger levels.
The Rugers however are NOT badly behind as CAS/SASS games guns (esp, with the freewheel conversion which is match-legal) and are worlds ahead as general field/ranch guns.