I have not used the new alloy version of the Hudy so I cannot say for sure. But as far as the plastic version....for me I would set the car up and if I checked it again a few minutes later it could be off sometimes as much as a degree or two! So I never knew how accurate it really was. The team magic gives me the same reading every time and is much easier to read for me.
The older hudy style on my Mugen, the hubs would never click in (in the rear) so they could easily slide back and forth on the axles changing your readings. The tm version however is very snug and stays locked.