Is the best salah the longest?

Assalamualaikum. I want to ask that is it true that the best salah is when you stand the longest… Is it true? And why is that?

Alaikumassalam wa rahmatullah,

The reward for a good deed depends on the effort and sacrifice we put into it. So standing longer in prayer is better because we spend more time and effort and we sacrifice more of our leisure for its sake.