5 minutes vs 10 minutes blitz game


What is the best to improve your chess level ??
How many rating of difference can there be?
Why are they both considered blitz game when actually there is a lot of difference?
There has to be a limit on how many time controls are offered because there could easily be some controls that wouldn't get enough players to constitute a ready pool of available players.
But there were 3 live chess ratings when they started and there are still only three--despite there being 14 different standard live chess time controls at the present time.
The more the time limit, the more time you will have in a game to think out your moves. Indeed, 10 minute games do have a different feel compared to 5 minute games or even 3 minute games which are more fast paced (one moment you play 1. e4 and in a few moments you find yourself losing on time).
However, it's quite difficult to categorise the classification of the time controls. In some other sites, 10 minute games are considered rapid other than blitz.