We have had two Flexa beds in constant use for 17 and 19 years. Over the years they have been L-bunks, high sleepers, and regular beds. They are still in use, only the mattresses have had to be replaced. I've offered 6'2" ds a new bed, but he likes his Flexa!
They were expensive, but were a very good investment.
We have stayed at places with bunks and our observations are:
Wooden bunks are quieter and more solid than metal, because you can tighten the bolts.
Flat slats on ladders are more comfortable for bare feet than narrow or round slats.
If you have the headroom, make sure that the bunks are high enough for an adult to sit on the lower bunk. If the ceiling is too low for this, get bunks that can be positioned in a L shape.
If you're investing in expensive bunks, get the sort that can become single beds.