Plot/keep track them both for a week or two and then decide for yourself. That's what I did.
I used to use the RTH classic pivots (H+L+C)/3, but found that getting the numbers off the CME's website was so convenient that I gave the all session data a try. The numbers are usually very close, except the all session ranges between pivot lines tend to be a bit larger, because the RTH will sometimes not take out either the previous overnight session's high or low. When it takes out both overnight high and low, then RTH and all session pivots are identical.
FWIW, I think the settlement sheets they post around the CME are virtually identical to the settlement page on the CME's website, which as you stated is all-session data.