there are so many variables to this, the question can not be black and white.
i have over 300k on my trans and motor, i have had way more motor related issues, and repairs. the biggest issue i see is people not maintaining their transmissions, basically ignoring them, and that will kill a transmission, i mean how long do you think your motor would last if you never changed the oil? and heat is the biggest killer of transmissions. the stock cooling system for a transmission is designed to keep the fluid around 190*, thats more than hot enough and close enough to a danger area if you ask me. roughly 112-114* is considered operation temp for toyota transmissions -basically if it will shift into overdrive its up to operation temp. so with that said, you are roughly 70* over required temps, if you can drop your trans temps down to say 150*(a happy medium) the fluid will not only last longer but give you much more room for dealing with heavy loads ie towing, driving off road ect. then you couple that with flushing a transmission every 60k or so and you should never have any issues with an automatic transmission on any vehicle. people pay $40-$80 per oil change every 4-8k miles but will bich about $250 to do a trans flush... do the math people, even if you go the longest intervals between oil changes and pay the lowest cost its still cheaper to do a trans flush at 60k than it is to do all those oil changes...
so in short there is no "one" answer to this question. although i do think that typically the motor will last longer just because most people spend more time and effort on motor repairs and ignore transmissions. but thats not to say the transmissions wont last.
