I don't have one myself but from what I've read, they all perform at a similar level and the thinner the walls of the ball chamber and the closer the balls end up to the bud in your bowl, the better. Basically as little unnecessary material as possible as that just dissipates heat (freight train is a good example for how not to do it). Metal for the ball chamber generally outperforms other materials although the quaroma is supposedly pretty much the tastiest option in that form factor.

Cloud connoisseur zeal seems to be one of the best options for price/performance ratio rn.

But again, all second hand info here, maybe someone more qualified to answer the question will show up.