Both has pros and cons.

Central:
1) Takes longer time to boil / keep warm -> more electricity
2) Provide continous steady stream of warm water. You don't bath in hot water    Hot water is to process dressed-chicken.

Individual:
1) Almost immediate warm water. Sometimes too hot and boil off the sausage/fish-ball/double-pau
2) Irregular temperature, fluctuate. Which will make you turn the heater up. Then... refer #1 

Best is, install another separate tank on top of the roof, either black PVC or metal is fine, as both absorb heat. Let our natural sun become the heater.
Unless most of your team take bath at similiar time, otherwise don't go for central.

Another way to look at it, you don't use a 5L kettle to boil water, then make a cup of 50ml espresso.    It would be better to use the small 1.2L jug to boil and faster too. Save electricity.

Unless you plan to boil 5L water, then make 2-3L of hot coffee/tea for a gang. 

The tank on roof will provide warm water on sunny days and if bath around 5pm-8pm. If water not warm enough (e.g. you always come home 11pm) or on rainy days, I suggest use individual heater if really want to. There are other consideration as well, low water pressure, need pump? Extra tank on roof use same piping or new piping ? cost ?

If want cold shower, one way is to buy a small crushed-marble/white-plaster tank. Old fashion type. Not plastic/white-PVC. Use the small-bucket (cedok) method. But must fill it up with water in advance 3-5 hours. Marble (like marble flooring) will cool down the water. To double/triple up the functionality, you can also use it to flush toilet or rear some fish/tortoise in it 

It may sound impracticle or ugly though... depending on preference for greener world or look nice/design. E.g. wear coat/jacket + tie walk outside the sun at klcc. Sure look proper and smart, but sweat like an idiot.

Side track: I don't like those designer/architect who build full length glass wall/window for homes. It is just plain stupid to have the sun shining, and you pull the curtain to cover it. The heat build-up will require more air-cond. Yeah yeah, it look nice, but impracticle. If we're living in Scandinavia, then full length glass is alright. But no, not here in M'sia with 4 seasons of summer.