I’d probably get the Highlander as it’s not only cheaper to maintain, but it doesn’t have as much transmission issues as the Acura even though the Highlander 2017 and up have that 8 speed auto. Even with that 8 speed, there haven’t been major issues with the Toyota. Just make sure a good mechanic checks it out before purchase.

I would look at the Toyota Highlander especially if you need it to last you for as long as possible.  Not sure if that particular Acura MDX has AWD, but Scotty has already mentioned in the past not to get the AWD Acura’s if you plan to keep for a long time and put as much mileage on it as possible.  AWD is not their strong suit, and expensive to repair over time.  The other knock against the MDX is the 3.5L V6 has cylinder deactivation (or what Honda/Acura calls VCM - variable cylinder management) and over the long haul there is potential for engine wear/damage.  It’s another layer of complexity that may become a liability over time.  Then the engine is direct injection-only and over time is susceptible to carbon buildup on the back of the intake valves;  you can mitigate by installing a catch can (and will have to empty it of oil from time to time as well as remove it for states that require smog/state inspections - another maintenance item) and even then may still have to clean the back of the intake valves periodically (on the order of every 60,000-100,000 miles) - again just more maintenance.  It’s not a dealbreaker as most engines are direct-injection only but something to be mindful of.  Toyota’s, by contrast, have none of these shortcomings just mentioned.  Then, absolutely avoid the ZF 9-speed automatic transmission which unfortunately was standard in the 2016 and up Acura MDX;  ZF normally makes good transmissions but that 9-speed has just been a disaster no matter which vehicle it is in.  Currently with the exception of the Lexus LS and LC lineup, no Toyota product uses more than 8-speeds for their automatic transmission (although jury out on its longevity as well).  Given all this, stick with the Toyota Highlander.

Personally, I owned an early 2ng generation MDX and it was amazing, gave it to my brother in law when it had 360 000 miles, it now has 586 000 miles on it. 

I recently purchased the 2013 Toyota Highlander AWD v6 just because it has true fulltime awd, unlike the 2014 and new with fwd to rear only during certain conditions. I live in Central Ontario in the snow belt, we get tons of snow, so fulltime awd was more appropriate for me. My one big quam about the highlander is that the seats are firmer than i would like, but they are comfy. You couldnt go wrong getting either vehicle, but the Acura is more of a sporty crossover that is very nimble and quick and fast and very upto date with all the recent tech goodies, whereas the toyota is still spritely with the v6, it is much more conservative with both design and tech available unlike the MDX. Good luck on your purchase, the toyota will have best resale value though. That is for sure!