I've had abt 12, and it's a scrumptious beer, but not the other 3.
Abt 12 is my favorite out of the bunch, but out of the 3 I've just recently tried Pater 6 was my favorite. Not too sweet, good biscuity taste, the bubbles were mild when drinking (idk but belgians foam up like crazy when I drink them, tripels dubels and quads at least), and would buy again If I ever seen one exist outside that gift box.
The tripel and the Prior 8 were fairly similar afiak, good beers, but a few tiers below the pater 6 and abt 12 in my opinion.
One bad thing I've been getting into is geuze...

I hate how much I love these. Only had geuze boon, geuze tilquin, and pictured oude geuze fonteinen.
It really sucks because geuze boon is the cheapest (and hasn't been available in over a year) at $12 per 12oz bottle...and this oude geuze was $15 for a 12oz...
I will limit myself to 2-3 a year out of sheer stupidity of cost, but these things are delicious. I need more.