KV-1.
The PZ-III and the KV-1 have the best suspension of the metal tanks. Other torsion bar suspensions ones are good, but not as good.
Their Tiger, KT, JP/Panther torsion bar suspensions are good as well, I just think the PZ III & KV-1 are the best of them.
Plus you can buy them as an off the shelf unit with steel gearboxes, metal running gear, torsion bar suspensions, and a latch hull attachment system (for easy battery & smoker access).
That being said, my son's Heng Long King Tiger is running on stock plastic HL gearboxes for over 2 years (all plastic driveline, running gear and coil spring suspension on plastic arms). It can hold it's own fairly well!