Go through that thread and decide for yourself.
There's such a wide variety of great triggers available that it pretty much becomes opinion based.
These types of threads are typically not allowed, as people start to argue when someone doesn't agree with their recommendation.
That being said, I'll leave it open for a while and see how it goes.
PS I fixed your title. I changed it from "what trigger should i get for and ion." to "What trigger should I get for an ion?"
PPS I recommend the Critical RPM trigger. It's a little pricey, but out of the 4 or 5 different triggers I had, it was the best.