My feelings on this matter are strong enough to have compelled me to create an account in order to post this reply! From my experience, I would strongly advise against the MDB4949. We replaced ours in less than a year, because we were so fed up with it! Inside that year, we had to have the wash motor replaced to boot.
Any cycle shorter than PowerBlast + Sanitize (at 3h48m total time, without Heated Dry) was guaranteed to leave behind even the simplest deposits (and don't get me started on dried ketchup or melted cheese). Even when running that super long cycle, which I've heard consumes over 10 gallons of water, we would still end up with redeposit soil on the *inside* of tumblers and mugs.
I was also fooled by the "most powerful motor" claim--when the replacement motor came in, turns out it's rated at the same 1/6 HP as all the rest of the Whirlpool-manufactured machines, it just appears to be connected to a slightly larger impeller.
We ended up moving to the GE PDT845 when they went on deep discount for pre-Black Friday. The bottle jets were a driving force in that decision, and while they do work splendidly, it makes for kind of a strange configuration on the rest of the top rack--there is one row of tines that won't really fit anything but cooking utensils, even Corelle coffee mugs are too wide! Speaking of Corelle and racks, I have actually gone off and carefully bent the tines (of a $1,000+ dishwasher) on the front row of the lower rack about 7-10 degrees to the left, in order to allow a full batch of cereal bowls to fit properly without nesting. (The manual says bowls go on the right of the upper rack, which is impossible if you're using the bottle jets; they share the same physical space.) It also struggles a bit with redeposit, unless we treat the (admittedly easy-to-access) filter like the lint filter in the clothes dryer, and rinse it after each load. If your diet is heavy on beans, this will drive you crazy, as bean fiber is just the worst for it!
I have no experience with the recent Whirlpool-branded machines, but my instinct would be to shy away from that TotalCoverage spray arm. It looks like a lot of moving parts interacting in rather precise ways, in a relatively harsh environment. This is the same logic that steered me away from the LG QuadWash. The GE reversible lower arm uses a passive diverter, and the motor will stop/start to increment it from one outlet to the next.
All told, I would almost go back to our original (pre-Orbit) Frigidaire which had the most usable rack space and layout, alternated spray arms by reversing its motor rotation, and produced consistently immaculate dishes because it ran a brief fill during each drain cycle to rinse debris off the filter! Four motors shredding their bearings over the course of six years, though, still leaves a bad taste in my mouth.
