Can your DD/DS climb the ladder alone confidently with little chance of falling? That for me would be the marker. Bunks usually have a barrier to stop you from falling out.

We bought Liebling a cabin bed for his 5th birthday (dull parents). When shopping for it, he struggled with the ladders for normal bunk beds, but could manage the sloped one for the cabin bed. He could do the flat ladder now, but I'm not buying him another bed.