How do they compare against each other? PSM vs CSM?

First and foremost, I would like to clearly establish the fact that (according to me) both PSM and CSMwould be really helpful with your career transition, into Scrum Master Role. There is no doubt about this. 

However, if one really wants to compare one against the other, there are a few things that I would like to highlight. As one can see, PSM I has a challenging time limit as it comes with a single attempt ONLY and has a hard pass mark, while for CSM; time limit is not very challenging as you need to answer a lesser number of questions and you get multiple attempts too. 

There is also a general perception that Scrum Alliance certifications are typically better known & recognized by US-based companies, whereas in Europe, Scrum.org seems to have a much bigger presence but there is really no hard evidence to prove this.

In short, my PSM "journey" helped me to know what Scrum is actually about. It seems to be more real world - in practice but you will always find people calling out, that there is less proof of training. Probably it’s just me & my wishful thinking.

Certification Common Factors	CSM offered by Scrum Alliance	PSM I offered by Scrum.org
Cost	Over $500+ (varies for different training centers)	$150
Validity	2 years ONLY. Thereafter needs to be renewed every 2 years, at a cost of $150.	Lifetime. No renewal needed.
Exam Questions & Duration	50 questions and a 60 minute time limit.	80 questions with a 60-minute time limit.
Pass Mark	74%	85%
Number of attempts	Multiple (first 3 are free and every additional attempt is $25)	One attempt only (although an additional free attempt is given to those who attend the PSM training, in case they fail to clear the test in their first attempt)
Difficulty of Assessment	Easy (almost impossible to fail)	It’s not straightforward so needs an intermediate understanding of Scrum.
Classroom training & course material	Mandatory course offered by CSTs.   Course materials also vary significantly in both content & quality depending on the instructor.	The course is NOT Mandatory but there is an optional course offered by PST’s in case you need one.   Pretty standard course material owned by PSTs and created by Ken Schwaber.
Number of Certifications issued till date	There is a no clear number published by Scrum Alliance but this will be way higher when compared to PSM I.	221,837