I didn't even know there was an SXT model until I came on this site. I know in Canada, there is no SXT model. I realize you're in WA though. From looking at the exterior of the SXT, it looks like there are no fog lights. That may be an option you can get though. I know with the SLT/Adventurer/LTD, the fog lights are included. I think the SXT has cheaper wheels, and a black bumper too instead of a body color bumper.
I'm sure there are others who can explain the differences much better than I....
I am getting around 300 miles per tank of mostly city driving.
The main diff's I have come to realize are some interior accessoiries.
NO OVERHEAD CONSOLE
NO FOG LIGHTS
SPEAKERS ARE COAXIAL, NO TWEETERS IN THE DOORS.
I have a 4.7 (SLT, 4x4). Just finished a 3,000+ mile roadtrip, loaded down and pulling a popup camper. Got about 15-16 mpg. Plenty of power, though, even over high mountain passes. I've gotten as high as 19 mpg on the highway without the trailer. City driving usually gets me about 15.
The SXT is really just a slightly enhanced ST and does not come with a third row seat standard, but can be ordered with one as an option. It's offered as a 2wd or 4wd, and with a V6 or a 4.7-liter V8.
The SLT adds body-colored bumpers, chrome side mouldings, larger alloy wheels and tires, a standard roof rack, woodgrain trim in the dash, much more plush cloth on the seats, and of course the standard third-row with rear air.
There is some overlap in the pricing which allows you to get a Durango SXT with a V8 and third-row/rear air for the same price as an SLT with a V6. To me, the SXT is the better value there.
In the 1st generation Durango the SXT had an appearance package (fog lights, running boards etc) that made it look every bit the part of an SLT with options - HOWEVER, the previous generation D SXT offered only PART TIME 4WD for loose or slippery surfaces only; thus the wheels are locked in 4WD and can not turn at different speeds - one wheel must slip when they are not going in the same direction. You can tear up driveline components quickly if you engage a 4WD PART TIME system on a surface that does not allow enough slipage.
Again, this was true of the first generation Durango - I am unsure if this is true of the new/2nd generation but I mention so you can be sure to check it out.