Same chassis, bodywork, and engine for both years.
Notable changes for 2016:
-Team clutches that are more reliable, but it's been argued that cat secondary from 2014-15 performed slightly better.
-New skis that floated better but were more twitchy and unpredictable. Both years need upgraded skis.
-36" ski stance with revised spindle angles (2015 has 38" ski stance).
-Redesigned rear skid. Different rail profile, longer front arm shock, and revised leverage ratios.
-Limited model came with Float Evol shocks. Sno Pro models in 2015, 2016, and 2015 Limited all came with standard Float shocks and coil over front track shock.
-Limited model came with a 3" powerclaw track. Noticeable improvement over the 2.6" powerclaw (used 2013-2015) in most conditions. The 2.6" is probably the toughest track ever produced and can still handle high speeds down the trail if you have to ride a lot of trail and less than epic snow conditions.
-Limited with 3" track used 7T drivers and was geared down too far with stock gearing. Re-gearing the sled or swapping to 8T drivers is mandatory to get the most out of it.
-Limited model came with a much nicer seat with good storage.
Between the two, I'd really try to get a 2016 limited if you can.
162 will allow you to go slower and take more time picking your lines. In deep snow the maneuverability difference isn't a lot different. Low snow the 153 is easier to throw around. Also if you're 225lb or more the 162 planes out much better. 153 would be my recommendation for you, but I have a friend your size that won't ride anything but the longer sleds because they are more capable in deep snow.