Difference Between a V1 and V2 Hotend?

I know that Zortrax recommends the use of a V2 Hotend with several of their filaments as opposed to the V1 Hotend. I note that the local store sells a V2 and that it specifies that the thermocouple and heater tubes are not included. I assume that this because they are merely used in the V2 upon installation. The only other difference that I can see is that the V2 has more mass than the V1. It looks to be about 50%. Now, this makes sense if the intent is to smooth out dT and keep the nozzle at a specific temperature. Any other insight out there that I do not understand?

V2 have also PTFE tube.

I've never compared the weights, but I doubt the mass of the block differs by as much as 50%. As Aleksiej mentioned, the major difference is the plastic insert, which reduces friction and keeps the filament cooler in the downtube. I've run a V2 tube in a V1 block and not noticed any difference in perfromance between that and the completely-v2 setup.

Thanks Julia. By V2 tube do you mean that you've put the PTFE tube only in the V1 block?

Yes, the v2 downtube assembly (stainless tube flange, plastic insert) can be mounted on the v1 heat block. For some reason I forget now, when I received my first v2 hot end it was easier for me to swap just the downtube and keep the original block than to change over the whole hot end. When the v2 hot end was first released many people had issues with reaching final temp (possibly due to the finish or oxidation of the v2 block) but I never had those with the v1 block.

Slightly larger mass and a set voltage is what caused the 99% heating issue. The printer could not allocate more power to the hotend, it was patched a month or so after the problem was confirmed.