ATF Compabitility Conundrum

I'm getting ready to do a drain/fill w/ filter in my '01 transmission with 270k. I've had this truck since August, PO kept decent records and one of them indicates a transmission drain/fill about 40k ago, but the garage that did the work lists that they refilled with "ATF 134." Looking into it a little, that appears to be an ATF grade specifically marketed for some Mercedes transmissions, and is specifically stated to NOT be backwards compatible with fluids of MB236.15 or earlier specs. Of course, MB236.15 is a Mercedes standard, and it all gets a bit fuzzy with what fluids meet that spec due to the localization of certain standards across countries. Google has inconclusive results.

I'd like to use Valvoline Maxlife ATF, because I've had good experiences with it in the past, and it's not a million dollars. I'm also thinking the Maxlife will have added goodies for this high-mileage unit that the ATF 134 does not. As I'm just doing a drain and fill, I obviously won't get all of the old fluid out. Has anybody had experience with this before? I'm leaning towards just going for it but I don't have the bread to rebuild a transmission right now...

 

I'd just use what meets spec, previous drain/fill's weren't complete either.