The Elite Heavy Stormtrooper has mostly the same stats as the regular version. He has more health, but in the end both Units have 2 health per point. In addition the Elite has better Surges, but the combination of 1 blue and 1 red dice doesn't show that many Surge results, therefore this is no great bonus. Some great Command Cards have a point maximum, that is easier to meet with the regular Version, e.g. Elite Heavy Stormtroopers cannot use Reinforcements (Reinforcement Cost max. 3).
Therefore, the elite version is relativly unattractive when compared to the regular one. Furthermore, the 8-points-slot can be filled with either a unit of regular Royal Guards or an elite E-Web. Therefore the Elite Heavy Stormtroopers will play no further part in this comparison.
The Elite Stormtrooper and the Regular Heavy Stormtrooper have the same cost per model / reinforcement cost (3 points per model).
Since passing is allowed, in my opinion, 3 figures for 9 Points is better than 2 figures for 6 Points. The Opponent has to kill more figures to get the points. The chance for using Reinforcements to full effect is better. Command Cards, that effect an entire unit, are more efficient. If you have the initiative on turn two, then a 3 Trooper activation is more effective than a 2 Trooper activation.
Elite Stormtrooper +1
Both the Elite Stormtrooper and the Heavy Stormtrooper have the Trooper keyword. Additionally, the Heavy Stormtrooper has the Heavy Weapon keyword, which is great.
Heavy Stormtrooper +1
Speed 6 is great. Speed 5 is good. Speed 4 is OK. Speed 3 is for dwarfs.
Heavy Stormtrooper -1
2 health per Point is on par with Royal Guards.
Heavy Stormtrooper +1
Heavy Stormtroopers have Composite Plating. Currently, most attacks come from 3 or fewer spaces away. Therefore, this ability has next to no effect at all.
Heavy Stormtrooper +0
Both Squad Training and Last Stand are great.
Elite Stormtrooper +2
A red die with "Surge: 1 damage" deals the same amount of damage as a green die with "Surge: 2 damage". A blue die with "Surge: 1 damage" deals less damage than a blue die with "Surge: 2 damage". Not counting the blast, the Elite Stormtroopers deal more damage. The green die has a little less average Accuracy than the +2 of the Elites.
=> More figures in the unit, more mobility, more Damage, better special rules … this one goes to the Elite Stormtroopers.