Winglets vs Sharklets vs Blended wingtips
Winglet advantages


With a winglet you see a 3-5% reduction in drag which helps increase efficiency in aircraft by reducing something called a wing tip vortex which forms by the high pressure(under the wing) wraps around the top part of the wing which has the low pressure and results in a wing tip vortex. A winglet works by deflecting the air so less high pressure wraps the wing tip.
Increases lift(the winglet generates lift also like an aircraft wing)


Winglet disadvantages


Adds about 300 lbs of weight to the aircraft depending on the winglet
Reduces maneuverability which is why you don't see a winglet on a fighter jet


Now a sharklet and a winglet are essentially the same thing.

Bts: Its called a raked wing tip

Raked wing tip advantages


Does the same thing as a winglet by deflecting the air. With a raked wing tip you actually see a greater drag reduction than a winglet can give you which leads to great efficiency in aircraft


Raked wing tip advantages


You actually loose a little bit of lift due to the raked wing


Sharklet- The sharklet deflects air just like a winglet and acts in the same way and is a winglet, but Airbus just named it differently.

A350 design- The a350 uses a sharklet and a raked wing. You see great numbers of efficiency in the design because you include a raked wing and a sharklet.

Between the 3 you mentioned there is a big difference and all 3 have different advantages and disadvantages. They all act in the same way by deflecting the air the design is just different for each one. I hope this helped you understand a little bit more about these devices.