Lots of experience on this one
I will talk about the Taigen tanks, ie the KV-1, Tiger 1 and King Tiger Henschel turret.
As far as I am concerned the rest are the same as Heng Long BUT they are complete. What I mean is a Taigen tank say a Panther is out of the box ready to run do nothing, so is a Heng Long but it has the cheap RX18 and crap paint job - Taigen is DONE. You run it and it is that simple. Great tanks for beginners.
So the real TAIGEN tanks in my opinion are the ones with the upgraded suspension and metal parts. These are Unique to Taigen and nobody else. ( Tamiya has quality metal parts but I do think and can be corrected on this the Taigen is more metal as a general product)
The fit and finish is great, they are solidly built and ready for the most part out of the box ( Plastic version Tigers need paint but little else ) the metal version tanks have a value above Heng Long and dare I say from a cost point close to equal with Tamiya and in some areas better.
The worst part of the Taigen tank is the electronics and I don't care what anybody says in my opinion they are the same as HL's 2.4ghz. Taigen only fights Taigen which in my book is a huge handicap as I am an IR battle fan and I hate airsoft.
The sounds are not good and niether is the control of the tank.
At the end of the comparison though you can replace their electronics and radio for $150 bucks, you add that to the cost of any tank and compare the value ( Note I said value here, there is a huge difference between price, cost and value ) I am sure you would have to admit that it is worth owning one.

Note I am a distributor of Taigen products so I am biased but this bias has come from working on them, fixing them and upgrading them. take my opinion as just that - an opinion.