well it depends. With the A64 the memory controller is on the cpu, so the memory performance is more dependent on cpu speed. but my question is, how high is your vcore at 2.4 and 2.6. With memory higher frequency is usually better performing than tight timings, but with the a64, higher cpu frequency is better.
the best way to test is if you have pcmark, run the cpu tests and memory tests only. Then compare those scores at 2.4 and 2.6, see which one you like better. but ill tell you now, chances are 2.6 with memory at 217 will prob perform better. good luck.