What is the difference between a snap judgement and evaluation?

A snap judgment is a compound word that comes from the word "snap + judgment". And as it can be easily seen and understood, a snap is a sudden, impulsive act, which makes the whole word "snap judgment" as a decision that is made without any second thought. The judgment made or declared without any further thought or discussion is known as a snap judgment.
On the other hand, an evaluation is a process where decisions are made after careful consideration and thinking through, unlike a "snap judgment".
So, the main difference between a snap judgment and an evaluation will be based on the time spent in making the decision.