From everything I've read, the VEPR .308 16" is the most accurate of these rifles, with the caveat that it prefers lighter ammo (145 grain and lower). These rifles can sometimes do 1 MOA, depending on the individual rifle and ammo selection.
The reason you want a shorter barrel is because an AK suffers a barrel whip when fired. A shorter barrel means less deviation at the tip as well as the bullet exiting the tube earlier in the whip. This means that shorter-barreled AK variants are more accurate than longer-barreled ones.
I do own a VEPR .308 in 16", but have not fired it yet. I find it to be an excellently constructed and handy, lightweight rifle. I chose it over the 7.62x54R version because the 7.62x54R version only has a single-stack magazine. The .308 version is double stack. The rimless cartridge design also causes fewer problems when feeding.
If you do go with the 7.62x54R version, DO NOT shoot corrosive ammo in these weapons! It is a royal PITA to clean corrosive salts out of a gas-fed weapon. I learned that with my PSL. You have to scrub the gas tube clean and waste tons of patches and solvent. You'll spend more on cleaning supplies than you will save in ammo costs. Save that stuff for Mosins that just need the barrel cleaned.
My ultimate advice, though, is go for the .308 version in 16". Other than hitting power (and .308 is still formidable), the .308 VEPR is superior in terms of accuracy and ammo capacity. There's also a much wider range of .308 ammo available. You can get good-quality steel 20-round magazines from Csspecs. The VEPR .308 can be either a handy battle rifle or a handy hunting rifle. It's lightweight and balances well.
