EDIT:
I had more fun using the DMR than I ever had using the Halo 3 BR, especially when directly compared on H4's Ragnarok. Few things were as frustrating as shooting at someone in Halo 3 as they casually stroll to my base, disregarding my bullets because of how inconsistent that thing was. I think the battles still play out the same (relatively, in terms of player positioning for shootouts), except in Halo 4 we have more reliability with the DMR than with the BR in Halo 3's Valhalla. Granted, a 2x DMR would've been the best option, but when comparing the FUN of it, I'd choose the H4 DMR over any iteration of the BR.
Also, take into consideration the wealth of options players have to escape/delay a fight (sprint, AA's, etc.) so it kind of balances out, but I think H4 Ragnarok plays better than H3 Valhalla because the DMR was a better/more fun weapon to use IMO.