IMHO, I don't think it makes a lot of difference which you use - I've never noticed any difference in the way they work...
Yes, DE is mildly unhealthy to breathe, reportedly long term chronic exposure can cause silicosis, which is a degenerative lung disease, sort of along the lines of the "black lung disease" that used to get coal miners... I strongly suspect that the occasional use that a pool owner sees is unlikely to be a big problem, especially if you try to keep from breathing it as much as you conveniently can, mostly by handling it gently to minimize the amount of dust created.
In theory some of the alternatives are lighter in weight, and / or go further per bag, but I've never heard any indications that they are any less of a potential health hazard than DE... (As a general rule of thumb, breathing ANY sort of dust is not a good thing...)
Gooserider