These are my opinions on my favorite topic and are not meant to trigger anyone.
There are really only two that matter in terms of scale (global). Triton and FM.
Triton is much more convenient for us in the US. I do not like their reporting and recommended actions, but more importantly, I do not trust them as much as FM. But this is preference. They were the first to do ICP on a commercial scale, and should be able to get decent results.
FM has shipping labels but not pre paid postage. Also, their shipping labels are printed to Coralvue but not to Los Angeles, which means we need to print out our own or wait an additional day for the results. The reason is that they have three drop off points which forward the tests to Germany, and depending on where you live, east coast makes more sense than west coast or Louisiana. The reason I am going through the hassle of printing the label and wait 7-8 days for my results is that I trust them trying to deliver the most accurate results. I also think they have the superior supplementation system (cost, flexibility, simplicity) and the reporting connects very well with the adjustments needed, and their knowledge database is very insightful. And they have a coral farm where they can test out their recommendations and continuously make improvements. However, they are not without flaws. Their support is not great unless Claude responds personally - which he does sometimes. Their ICP consultant model is a great idea, Reef Bum is one of them, but the ones I tried were not always that helpful. Lastly, there are continuously shortage with their product availability in the US which is painful.