For my comparison of these 2 cars I'm going to focus on the Rustler XL-5 model #3705 that is currently in production .
To start the average price of the Traxxas Rustler is around $205 + shipping and the Turnigy Stadium king will cost around $148 shipped . Its twin the ZD Racing ZMT-10 can generally be found for around $120 or less shipped .
References to the ZD Racing ZMT-10 pertain to the Turnigy Stadium King also.
Electronics as far as out of the box the Rustler Win's in almost all categories but most people should bare in mind your probable going to swap most of these items out with better equipment no matter what truck you buy. The rustler comes with all water proof electronics except for the receiver . The ZMT-10 doesn't .
The Rustler comes with a high current battery connector the ZMT-10 doesn't . The trucks in my opinion both have comparable radio systems that function well but the Traxxas system has a more modern look to it .
Battery's and chargers for both trucks leave a bit to be desired (but these are targeted for beginners )the ZMT-10 comes with a 2400 mah 6-cell battery pack and a 110 volt wall charger good for around a 1.5 amp charge rate. Traxxas includes a 3000 mah 7-cell battery pack( good for a 4-5 mph boost over a 6-cell ) and a very similar charger.
Tires and wheels are also important . Both trucks have 2.8 inch wheels with 12 mm hexes but use a different tire beads that seem to make make them in compatible . Even though I don't really like the newer Traxxas rims they are better than the ZMT-10's rims. The ZMT-10 does win in regards to tires . In my opinion they beat the rustlers tires when it comes to traction in the dirt . Given there soft nature they do wear rapidly when run on asphalt or concrete.
Drivetrain is also a bit different . The Rustler comes with full ball bearings and Traxxas's 272 magnum transmission with all metal drive gears .The ZMT-10 has 2 ball bearings and 4 bushing with full metal gears of a slightly fine pitch than the Traxxas transmission possibly making it more efficient but also weaker . Traxxas uses plastic slider shafts with plastic yokes for the drive axles . ZD optioned to use metal dog bones and metal drive cups in my testing they have held up great. Traxxas has started using there revo style slipper clutches and to be blunt its tuff . The ZMT-10 is using a more conventional pad based slipper clutch system that should lend to comparability with other brands spur gears and pads.
All that is really left is driving and to be honest there really isn't much difference the 2 are almost Identical with the only difference being that the ZMT-10 has a slightly shorter wheelbase but in my experience this is hardly noticeable .
I do recommend doing a little reading about the recommended upgrades for the Traxxas Rustler and remember most of the parts for the rustler are a complete bolt on for the ZD Racing ZMT-10 or Turnigy Stadium King 2wd Truggy .