Let's go more in depth to learn about HL racket design. Here, the terms Box & Aero refer to the shape of the cross section of the racket head portion of the frame.
As you can see the Aero Frame design curves to a point, and the Box Frame curves to a walled flat portion. The following are HL racket's that feature these frame shapes, properties of each, and which one is best for you.
Aero Frame - as the name implies, this shape minimizes air resistance. With low air resistance your swing speed will increase. When the shuttle is approaching fast, players will benefit from increased reaction time on their defensive strokes. An aero-frame can also help reduce fatigue as each stroke takes less effort to cut through the air. However the aero-frame isn't without compromises, the structure of an aero-frame is not as robust as a box-frame therefore missing the sweet-spot on an aero-frame is more likely to cause unpleasant vibrations. Further, an aero-frame transfers less power to the shuttle. Beginners playing a slower game may not see much benefit from an aero frame.
Who will benefit:
Doubles players often prefer aero-frames because of the need to react & change position of their racket quickly.
Intermediate and above players who are playing a fast paced game and often hit the sweet spot. These players also are unlikely to suffer from a decrease in power because they already have powerful hits.
Box Frame - the box frame gives the racket more structural integrity, thus making the racket more durable. Because of the shape a box frame offers more torsional stability, if you miss the sweet spot you won't feel as much vibration. Finally because the frame transfers more momentum to the shuttle you get more distance on your shuttle even from a slower swing. The downside is that the racket will not be as quick and defensive play will not be as effortless. For long periods of play with hard strokes a box-frame may cause more fatigue.
Who will benefit:
Singles players - the game is slower than doubles, and does as demanding in terms of reaction time.
Hard hitters - players who love to smash and want the most power.
Newer Players - these players hit the sweet spot less often and generally play slower rallies.