Heng Long and Taigen are basically the same company, like Toyota and Lexus, they just add all the upgrades to a standard Heng Long and then charge an arm and a leg for them, don't get me wrong depending on what you use them for they can be a good choice, but buy used they are not worth the new price imo.
Metal upgrades may sound like a good thing but it adds a lot of weight and will put extra strain on the gearboxes and struggle to run well on grass, I am a member of a club who meet up for IR Battles at various shows around the UK, most of us use Tamiya Tanks or Heng Long with after market electronics like El-Mod or DBC, we all use plastic tracks for better manoeuvrability which helps a lot after taking a couple of hits and the tank starts to slow down.
For your