Advantages/disadvantages for limescale cleaning methods?
Methods I know about:


Vinegar
potatoes peels
citric acid
Coca-Cola 
baking soda 


Each of them is actually better for different types of kettles.


for glass where lime is quickly visible or where there is large amount of lime. Con is the smell that require multiple washing. 
for kettles where heating element is not part of the chamber. Cheap and easy but con is that require multiple brewing changing peels with each one. 
Best for steel ones (but work for others of course) cons is that it need time to work (usually overnight) and shouldn't be boiled. 
very soft method, best for ceramic kettles. cons - it's coke and people may taste the extra sugary and additives for many brews. 
good for electric kettles or with exposed heater. cons is again, the after taste that require multiple boiling's and pouring out the water.  With very hard water you can end up at the same place when started. 


Apart form the coke all advantages is the price. They are all relative cheap and with peels you can just use some that normally would be thrown away. 

Citric acid with a little of water is best for prevention as you can just quickly wash it once every week.