My guess would be the "08" at the end of it. The same would be true for any calibre with an "06" at the end of it. Hunters have a comfort zone with the 308 and 30-06 so any calibre derived from them have the edge. 7x57, 6.5x55 and other "metric" calibres are not a big hit this side of the Atlantic. Hell we don't even like the sound of 7.62x51 in that form.

I think 7x57 has more market penetration than 7mm-08 at least around here. Neither has much.

The 7-08 is the "modern" 7x57. It can be loaded to higher pressure and you don't have to wory about the older, weaker Mauser 96 actions. There is High Energy and Hornady Light Mags for the 7x57. Both are pretty darn good rounds that will kill what needs kilt.

I believe, forum member remington, hit it on the head.The newer 7-08 can be factory loaded to the higher pressures of the newer rifles.
Not to say that the 7x57 is any lesser of a round but, they need to factory load it to meet the specs of the older rifles. Of which there are still a many in use.
The 7-08 is to the 7x57 as the 450 marlin is to the 45-70.

Being a homeloader. It would be a six of one, half a dozen of the other, choice between the two. The 7-08 would be the more logical choice, in these 48, with the availability of brass that can be formed, if needed.

I'd like to add that. Although not the best choice for any one particular scenario. Any of the 7mm's are fine rounds and a great one rifle hunter for a person that wants to use a single rifle for everything. From little critters to as big as they get, in these 48.
I believe the reason the 7mm's are not as popular as some other rounds. With the exception of the 7mm Rem Mag., is the availability of the 270 win. Also, the .264 diameter outshines the 7mm's in inherent accuracy and the .308 diameter hits harder with a bigger hole.

THE 7X57 HAS TO BE HANDLOADED TO MATCH

FACTORY LOADS IN 7-08 IS WHAT I HAVE SEEN

ON CHRONOGRAPHS.  BUT THEY ARE BOTH VERY

GOOD ROUNDS. ME, I WOULD PICK THE 7-08.

I think it's due to American hunters not really accepting non-American cartridges. You can put metric bullets in American cases and have a success but if you put established and effective Euro cartridges on the same market they will fail.

Many of our favorite cartridges are metrics, look at the .243 Win, .260 Rem, 280 Rem, 7mm-08, 7mm WSM and 7mm Rem Mag. Pistols are .380ACP and .40S&W.

Popular non-American cartridges are 6.5 X 55 Swedish, 7 X 57 Mauser, 8 X 57 Mauser, 7.62 X 54R and .303 British (7.7mm).