It's hard to say one headphone is "better" than another because of a single design choice. The difference between open and closed headphones is the decision to leave the backs open or closed. One style isn't "better" than the other but there are reasons and consequences behind each choice.
When it comes to air chambers, there are three kinds, maybe four. Closed cans seal the backs, much like acoustic-suspension loudspeakers. This creates the most isolation. It also allows the back waves to be used to reset the diaphragm. This design produces the loudest response, which is why it's a favorite among cheap headphones. Bass slam is strong because it has the backs to use as a kind of backstop. Unfortunately, such cans also have the most resonance to deal with. With nowhere to vent the drivers' backwaves, these phones have to utilize some damping technique or produce ringing, distortion or an overdose of bass.
Open cans go the opposite route. With the backs removed, resonance is greatly reduced. There's typically less bass but the quality of the presentation - from top to bottom - is clearer and tighter. Without the secondary waves (backwaves introduced into the presentation a fraction of a second behind the front waves), you get less output but the output tends to be tighter and clearer, with better detail, soundstage and clarity. Many audiophiles prefer open cans for this very reason. On the other hand, open cans leak bass and don't rely on backwaves to supplement the bass. As a result, open cans are less bassy but they can also seem bass lite.
One hybrid of the open/closed continuum is a bass reflex system. Many drivers contain a series of holes that radiate around the driver baffle. AKG famously used passive radiators in its K240 Sextett. When AKG replaced the passive radiators with cloth/air-covered holes, other companies followed suit. Now, a great many headphones that are advertised as either open or closed are actually using some form of bass reflex. This is similar to loudspeakers with ports or passive radiators. These holes help the driver vent some of its HF while allowing bass from the back waves to get mixed in. Some people like it, particularly where the bass on opened cans has been understated. Others dislike it, calling this bass "flabby" and "uncontrolled."
Another hybrid of the open/closed continuum is the semi-open system. A number of headphones that call themselves "open" are actually semi-open. That's because a truly open system, while it provides great clarity and detail, may struggle to provide enough bass or bass slam to satisfy consumers. There are lots of designs that reduce the "openness" of the open back in an effort to get a workable mix of bass and HF.
