I agree with Daniel R Hicks, my bell also gets a lot dampened in the rain, and this will happen with any bell.
But even so, some bell properties might influence:
- Steel is denser than aluminum, so a similar-sized steel bell could have more mass and ring longer;
- Bigger rings might also ring longer, because of the relation among size, mass, wall-thickness, and frequency pitch.
But, to be honest, I cannot say any of the above for sure, because I didn't test it.
If it is of any help, I use my ring upside down, and raindrops get inside it, but even so it rings just a bit less than dry (not a lot less).
It is a steel ring, the type that has a lever and a spinning mechanism inside (which I strongly recommend over the model you've shown).
Also, I have a set of similar rings on my bikes, and none of them has the same acoustic properties, I think there are some subtle factors involved, most probably the relation between the bell's main frequency and the frequency of natural resonance of the raindrops on the bell (I'm serious!).
Hope it helps