For the first time in my life, I think, I marked undecided, on anything.
To me both of these rounds have advantages and and disadvantages, and neither is an ideal round.
IMHO a good rifle round needs to have excellent accuracy, power/penetration, and can do that over extended ranges.
In fairness, the original concept, of these two rounds, was for basically short range. high rate of fire, light weight, carbine type use/weapons. They both do that well..sort of.
So I'd say get a couple of each, just to be sure you have all the bases covered.