I’d go with the P28A over the 26, Mooch’s testing shows the P26A only has a slight edge literally for the first few seconds at turn on after a charge, in all other instances the newer P28A excels and has slightly more capacity to boot (2600 vs 2800mAh).
I only run them in one light, my C8TT with triple LH351D W6’s, nothing else needs it / benefits from it.