Quoted:
which was the better weapon over all? accuracy, quality, reliablity, etc. the k-98 or the k-31?
Remington makes a newer k-98 currently.
I own five Mausers (three 98's, one 96 and a 95) and two Swiss K-31 rifles. I shoot the Swiss rifles pretty regularly. I rarely take the Mausers to the range. The K31 is more fun to shoot and more accurate. They've got great triggers. The Mauser's 8mm round is too stout for much enjoyable range time, the sights are crude and stock barely lends itself to accurate shooting. But if I were building a custom rifle, I'd start with the 98 action every time.
Does that answer your question? Of course not. You know why? Because it's an invalid comparison. The '98 Mauser is the basis for almost every centerfire bolt action rifle that came after it. It is the quintessential bolt action. The K31 is an odd-ball. It's cool, fun and remarkably accurate. But it's basically a dead end in the development of rifles.
So where does that leave you? In keeping with AR15.com tradition: get both.