A neighbor wanted a good but cheap guitar so I helped him choose one; we went to a store and picked the best-sounding and best-made among the budget ones. It's a small-size acoustic with the body of a classical guitar, the headstock and tuners of a classical, but a truss rod Inside the neck, like a folk.
After the stock strings became worn out I ordered some D'Addario's for him because they have always been great on my classical, folk, bass and electric guitars. I prefer those with medium-hard tension on my own guitars because they are not the cheapest, and made with full-size quality solid wood tops. Medium-hard barely feels different while it sounds snappier.
But I suspect my friend's guitar is not made with such durable wood so I chose the normal tension strings to avoid the risk of having too much tension on the bridge. The tone was fresher with more harmonics, not just because the strings were new but because the stock strings on a very affordable guitar can't be superb.
When my friend played it I noticed how the volume was stronger, too. They have no cosmetic defects or unevenness. We played them with a bone pick, fingernails of finger flesh, and the tone was always powerful and shimmering. The guitar is very okay for its price, and became better, nice grain, nice ring.
If you have a full-size classical with quality wood use the medium-hard tension, they don't really feel harder but sound punchier. I don't know about the hardest strings in the line.