Superflex vs Dicor EPDM

We are doing the same on our 1987 rv. I found the kit at rvpartsnation.com for 30 ft kit $423.95 thinking I'm paying for EPDM but you are forced to check the box before ordering... "they reserve the right to "upgrade" to Superflex"... if it's a lot cheaper & upgrade / better... why is there this message?? Feeling like I might should just order from Amazon. Curious what you guys ended up doing & how did it work out? Thanks in advance! <3
https://www.rvpartsnation.com/rv-exterior/rv-roofing/rv-rubber-roof/rv-rubber-roof-kit/