In my experience, the futon is unconfortable to sit/sleep on. The day bed was much, much better!
It really depends on the futon. Like mattresses, not all futons are created alike or of the same quality. Here in NYC, where space is minimal, furniture that does double duty is of utmost importance. This place has specialty futon stores. I've had FOUR different futons over the years because I love my convertible futon couch frame.
The first futon was the cheap, all cotton one that I think end up being most people's first futon, (especially college kids) because of the cheap price. It is all cotton and matts down after a couple of years to an incredibly hard rock and becomes uncomfortable.
As I started to have back issues, my second one was an orthopedic futon, with an inner-spring core. While, it folded up, as futons are meant to. It didn't occur to me to test out this part of the feature in the store. I only tested it for how it would feel for sleeping. As I left the store, out of the corner of my eye, I noticed a guy came over to help the sales woman fold the futon back into the "clam shell" futon/couch frame, (same as I have.) It didn't occur to me, until hindsight, that I should have gone back to see why he was helping her. I thought he was just being polite.
No, as it turns out, while the inner-spring makes it great for sleeping on, it turned it into a farce to fold up. it was like an episode of I Love Lucy getting it to fold properly in the frame. A regular futon will lay in any position you fold it. An innerspring futon wants to lay flat, unless held in a folded position. If not in the clam shell frame properly, BOING! It would totally pop out.

I was doing hand & feet gyrations, like the game Twister, to push the futon in while folding.



It NEEDS two people to close it. Not good if someone is planning on opening & closing it into a couch each day by himself.
I switched out finally to a better grade futon (no innerspring) and have bought a 4" memory foam topper. They do make them combined, but they are way too much money, in my opinion. An added topper works fine. BOTH are foldable & bendable. My frame folds up easily, the way it was intended. I actually like having the extra 4" height. It makes for a much more luxurious & cozy bed & couch. What the memory foam topper did to heal my back problems was incredible. I recommend one whether you're using a futon or a mattress.
My fourth futon & pad were simply a replacement of the third set. I love this combo. I got them both from
www.overstock.com.