I have used these fittings and I have no complaints. (link below) I used the plastic fittings on my first truck and I was constantly chasing leaks. On the next truck I used compression fittings like you described and while they never leaked they were more time consuming to assemble right.
I too use airridefittings.com, and my entire car for the most part is plastic PTC fittings, I daily drive it with zero leaks. I've left it up for 3-4 days, with out losing any pressure.