I have the option to fly between IAH and EWR on Monday August 25 on either flight # 210 which is a 767-200 or flight #1577 which is a 757-200. I will be on a discounted economy fair. My question is, which flight is easier for upgrade (I am a Platinum)? My understanding is that on these flights, it is nearly impossible to get upgraded, even for a PLAT.

Which flight do you guys recommend for me to take? Timing differences are minimal as the 757 leaves about 30 minutes before the other flight.