1a.Not all men are equal in ability.

1b.All men are not equal in ability.

2a. Each of us was not sick.

2b. None of us were sick.

3a. Stamp your work not because you are pressed for time.

3b. Don't stamp your work because you are pressed for time.

4a. They found the installation not up to the standard.

4b. They didn't find the installation up to the standard.

5a.They considered him not a reliable man.

5b.They did not consider him a reliable man.

I know each of the b is better than its'a, Is the 'a' equal to its respective 'b'? and is the a correct by grammar?(my very question)

For example, the "3b" is better than 3a, but, is 3a equal to 3b?

is 3a correct by grammar though 3a is less better than the '3b'?