When in Belgium, I found Westmalle dubbel to be the "go to" beer if the place didn't have a printed menu and wasn't particularly beer-centric. I knew without fail that I could easily order it and it would be great and would go well with almost any Belgian food I ate (their food is heavy and sweet). If I am slowly drinking 5 beers in an evening out (I am not usually a fast drinker), Westmalle dubbel and trippel are not too bold for me to continue enjoying and the high alcohol allows me to get somewhat intoxicated through slow drinking.
The bigger trappist beers that I enjoy so deeply like Rochefort 10 and St. Bernardus 12 are too rich to have more than one of, usually. Orval is a very specific beer. I actually far prefer it fresh over aged, so I don't really drink it outside of Belgium. Achel is okay, but clearly inferior to the others, aside from Koningshoeven. I think Koningshoeven sucks - like it is genuinely not very good beer and well below average in any beer bar in Belgium (yes I know it's Dutch). Westvleteren was very good, but not worth the hassle/$$$ - unless you can drink the blonde fresh.