Will reducing 1/2" to 3/8" in hot feed lower the p

[mestalla]

I am replacing a 6 litre heater on the balcony with an 11 litre one, to heat more hot supply. The new heater has a 1/2" exit. The pipe in the wall to a shower and sink is 3/8" but I cant get to it. So for max supply/pressure
do I reduce down at the heater or wait till the wall. The pipe length will be about 12 ft. in both cases. Thanks for any help, the heater is OK in the Winter, but not in the Summer.

 

[buck51]

The pressure should not alter, but the flow rate may be reduced,

 

[ChrisR]

If the flow was OK before then it should still be. Try whatever's easiest, first

 

[mestalla]

OK well thanks it seems there is not a lot of difference which way I chose.
I don't understand the logic of normally using 3/8" for hot water. I thought it was perhaps like a finger on the end of a hosepipe, the flow is the same amount but the pressure is increased