I have a 2007 Ridgeline and my wife drives a 2012 MDX Tech. No comparison really. The Acura rides better, handles better, better interior, less road noise, does not seem as big inside but I never ride in the back seats! The 3rd row seats are somewhat cramped but useable for kids or adults (if you don't have a long drive). We use the 3rd row seats maybe 1-2 times a month and it is fine. The cargo space when the seats are down is pretty good. Not quite as big as our old Pilot (2008) but comparable.
The Acura does take PREMIUM gas but the mpg is a little better (maybe 3-4 mpg average). I'm not sure if you do your own maintenance/repairs but the Acura will cost a little more. It's really comparing apples to oranges, they have almost nothing in common except the manufacturer.
Just as a side note, we were originally looking for a loaded 2014-2015 Pilot but many of the Acura MDX's were selling for the same price (or less) with more features and better overall quality. This was in August of 2015 and now with the new 2016's coming out the 2nd generation MDX's are priced to sell. Stay away from the MDX Advance, it has real problems with the adaptive suspension. I would also go with an ACURA CERTIFIED vehicle if you can; it comes with some extra benefits and these are usually low mileage leased vehicles or vehicles that were purchased and traded in before the mileage/year limits are reached on the factory warranty.
If you are seriously looking at an MDX then check these forums out:
Acura MDX Forum : Acura MDX SUV Forums
It is not quite as active as this forum but it has great information that will help steer you in the right direction.
Acura Care extended coverage beyond the original warranty
This is extended warranty information.
Respond or PM me if you want more information. Hope this helps.