The 7 x 57 mauser has been around since 1892 and I wouldn't call it "unique". I would be pretty confident in saying that there would be more rifles chambered for it than any other 7mm.
It can be loaded to exceed performance of the 7-08, and is capable of very good accuracy in the right rifle.
Just about every major ammunition manufacturer has commercial ammo for it. Some factory loadings are on the lighter side due to the fact that there are so many "antique" firearms chambered for it. ( 92 & 93 Mauser, Remington Rolling block, Lee 1897)
The M-98 Mauser is an inherently strong action and if in good condition would be capable of standing up to higher pressure handloads.
I have rifles chambered in both the 7 x 57 and 7-08 so speaking from experience not hearsay.
Actually just put the 7 x 57 barrel back in a Sako L61R yesterday and put 5 shot groups under an inch @ 100m with all loads tested.