One of my shooting buddies has an HK MR762 that I have shot a little bit. I'm not an HK rifle expert by any means (I do own some HK pistols) but here are my thoughts/some things to consider.
1. It was a very nice rifle in terms of fit and finish, definitely HK quality throughout. Accuracy seemed very good but I couldn’t say if it was better or worse than my SCAR 17, seemed probably about the same.
2. It is much heavier than the SCAR 17, but when shooting it the recoil is softer than my SCAR 17, most likely due to the added weight.
3. The gas piston system is not adjustable. So if you plan to add a suppressor it will be severely overgassed. That will cause premature wear and tear on an expensive rifle, and I don't believe there are any good solutions to that right now.
4. The factory trigger was probably better than my SCAR 17 but it still wasn't great. It definitely needs an upgrade for precision shooting and the Geissele trigger for it is $465, even more expensive than the Geissele trigger for the SCAR.
5. The barrel thread is M15x1 which is not very common, most 30 cal stuff is 5/8"x24. So if you ever plan on changing flash hiders, adding a brake, or adding a suppressor, you are going to have a very hard time finding something in that thread size. You could always have the barrel cut and re-threaded but then you are in SBR territory just to change a flash hider. I would also imagine there are some proprietary tools required to work on it in order to remove the barrel for threading.
6. Proprietary mags are even more expensive than SCAR 17 mags.
7. I don't think the non-chrome lined barrel is a concern for the rate of fire most of us will put it through. It's still cold hammer forged, and normal .308 loads aren't exactly known to eat barrels quickly (like the 6mm rounds for example), so it will probably last 10,000+ rounds before you see any noticeable accuracy loss. If you plan on doing mag dumps though then yes a chrome barrel is more durable.
So overall I think the MR762 is a very nice high quality rifle, my buddy is a big HK fan so I can see why he bought one. But if you were looking for a high end semi-auto .308 that was different than the SCAR I would instead look at something like the LWRC REPR. It has an adjustable gas system, takes a standard AR trigger, lots of barrel length options, standard barrel thread, takes PMAGS, etc. Otherwise if you prefer lighter weight and modular nature, all still with very good accuracy and durability, the SCAR 17 is a winner in my book.