there's no difference between 21 million bitcoin divisible by 0.00000001s and 21 000 000 000 000 bitcoin divisible by 0.01 but it sure as shit would be easier to use since it would be more similar to what everyday people use.

Bitcoin could keep a 2.5 btc reward per block forever after it reaches 21 million and it wouldn't have a dramatic decrease in value. Inflation isnt the issue, it's unpredictable inflation that is.