This is what I have surmised so far with this:
1) The Infinium does go deeper as it's a PI machine. That I already knew.
2) Discrimination to me seems more accurate on the Excal but of course like you said it does have a cut-off point unlike the Infinium.
3) It does look better balanced than the Excal. Most Excal users spends the $120+ for a lightning rod shaft to give it better balance,
4) The Infinium does not come with water-proof headphones. You have to buy those in addition to BUT the Infinium is about $130 cheaper than the Excal so you'd still be showing a plus in the wallet after buying a waterproof headset.
5) It does not come with a coil cover BUT I'd be using Marine Epoxy with a bed liner spray to
protect the coil. This makes it easier as it gets rid of falsing which I am not sure if that is an issue with PI but it was with the Excal with sand getting in between the cover & coil and having to continually clean it all the time. Plus it is cheaper than a coil cover.
6) Both machines can be used on Land. The Infinium weighs a .4 lbs. more but is better balanced.
7) I am not confident in the discrimination system used by the Infinium. It doesn't seem as thorough as the Excals. I will have to read the Infinium manual some more.
Eight) 10x14" is the largest you can put on the Infinium. The Excal is not interchangeable BUT I learned today from ML representative that any SEF coil could be hard wired by ML technicians at their tech shop. Not sure about the price. Still waiting to hear about that.
9) Both machines have their nuances with the tones and it will take time to learn them.
10) Garrett has a 2 year warranty whereas the Excal has a 1 year plus the 2 year ESP plan to give you a total of 3 years.
That's about all I could think of for now.