So between my dad, my brother and me I own two of the new Model 70's, my dad has 4 X-Bolts and my brother owned 2 X-Bolts but sold one.
My 2 Model 70's are both super grades in Win Mag cartridges, one in .300 and one in .458. The .300 was my original long range rifle that I learned to reload on, it is a quality firearm with good fit and finish that was accurate with handloads. I developed a 230 Berger OTM handload that shot under 1/2 moa when I did my part.
My dad's X-Bolt Eclipse in 6.5 Creedmoor is a tack driver and consistently prints groups under 1/2 moa with Hornady American Gunner ammo. His .30-06 White Gold Medallion shoots under 3/4" with a 150gr Superformance duplicate I handload, with actual load work I'm sure I could reduce that down even more.
He also has an X-Bolt Pro in 6.5 PRC, the first one did not shoot well and was sent back to browning and they replaced it. The new one shoots much better, did not get to do load work ups for it yet but I used the same target load I was using in my PRC and made hits out to 1000 yards on an 18" circle using my dope.
My Brother had 2 .300 WM X-Bolts but the second one did everything the first did but better so he sold it. His is a Hell's Canyon McMillan and while it loves Hornady Full Boar and Outfitter ammo it does not shoot the Precision hunters well. This rifle is on my list to start reloading for.
So in all honesty it is hard to go wrong with either though the browning does offer more long range options than the Winchester which seems to have relegated the Model 70 to purely a wood stocked hunting rifle which is a crying shame if you ask me.
No question about that but Winchester has not made a 30 caliber purpose built long range rifle since they dropped the Match rifles decades ago.
Browning does, out of the box.
I would have bought a Maple Super Grade in .264 years ago if they offered it in a faster twist and I absolutely would have bought a heavy barrel target rifle in .300 WM had they produced one. I guess my Pre-64 bull gun in .300 H&H with an Unertl scope is as close as I will get to a "Modern" Model 70 target rifle.