Pros of legalism are: There were much fewer crimes in china and the laws taught the people to act better.Legalism is a pragmatic political philosophy synthesized by Han Fei. With an essential principle like "when the epoch changed, the ways changed", it upholds the rule of law and is thus a theory of jurisprudence.
The Cons however, are the laws were VERY strict and usually had extremely harsh punishments... it also produced a dictatorship.
Hope this helps!! :)