Big rain shower with instant hot water, you will face 2 possible problems:
1.Water pressure not strong enough, so the flow of the rain shower will be slow.
2.Water pressure strong (maybe you have household water pump), but the instant hot water can't heat up the large volume of water.

If I just need hot water for shower in 1 bathroom, does it still make sense to go for storage water heater? Currently I'm using Joven instant water heater. I'm quite satisfied with the temperature as I don't really need very hot water for shower but I want to change to big rain shower for personal enjoyment. So far when I read in this thread seems like instant water heater is not recommended to be use big rain shower? or do you guys know any instant water heater that I can use with big shower head maybe like below type?

If I just need hot water for shower in 1 bathroom, does it still make sense to go for storage water heater? Currently I'm using Joven instant water heater. I'm quite satisfied with the temperature as I don't really need very hot water for shower but I want to change to big rain shower for personal enjoyment. So far when I read in this thread seems like instant water heater is not recommended to be use big rain shower? or do you guys know any instant water heater that I can use with big shower head maybe like below type?

rain shower does not need high pressure water.

if water pressure is enough for normal shower head type, it will be enough for rain shower system.

Your instant heater pump cannot coupe with this big shower head. It not enough power to pump the large amount of water for this big shower head.

The most bigger size for instant heater is 7" head. The istant heater have to design for the shower head, Not any instant heater.

Another problem is the water temperature will drop alot. This is due to

1) high flow water cannot absorb enough heat from the heater.
2) Because of the slow water drop from shower heat, the water been cold down by the air between the water travel from the head to your body. You can feel the water colder than using the hand shower.

Use water heater tank.

do u guys recommend wall mounter instant water heater or storage type water heater? what are the pros & cons?

Whatever you buy, don't buy Panasonic. Other than the brand, it worth nothing.

Hydro1 have 30L, 50L and 80L. Check at the Specification.

Base on the Eco30 L, 36min - 44°. If reach to 70° will take  - 70/44x36= 57min.

Base on Eco50L, 45min - 44°. If reach to 70° will take - 70/44x45= 71min.

Base on the Joven JH35L, 60min - 70°.

Base on the Joven JH50L, 90min - 70°.

May I know what's the current problem with Panasonic heater? Im planning to buy one since many quoted this brand. Thanks.

Pro:
Can supply to several bathroom
With high water pressure (high water flow rate), the water is still warm enough.
Faulty heater element hard to replace (on ceiling). Water wet ceiling during replacement because not all water in storage can be dried up (my own experience  )

Con:
More electricity if it is kept on, otherwise, the heat loss is just waste of energy during off state.
You tend to fully blast the water at high flow compares to instant water heater, thus water waste.
Normally use copper piping for hot water. How to channel to several bathrooms without major hacking?

I have both storage and instant. Storage in master bedroom because the house came with copper piping in the wall already. The heater element will corrode over time and cause power trip in the heater line. Many shops or service people  told me that usually people will replace will new tank. Well, I'll stick to replacing the heater. Bought it for RM90 (if not mistaken). Was unable to replace it because location too tight to put my spanner. Just called a person that familiar and he devised his own tool to make his work easy 

I only switch on when I want to use just like instant water heater. It does not take much time, probably less than 30s to start feeling the warm water. Keeping the heater on assuming like hot water pot increases electricity bill probably RM20~30. The heat retention is just not good I think.

hi, you seemed very well versed with storage heater type.  can i seek your advice on which is the best brand for about 50L storage.  and where can i buy?  and would you be able to recommend installer too?  much appreciate your advice.

Anyone know what is the reasonable labour charge to dismantle existing water heater & install a new one?