This might be slightly off-topic, but just in case it is of interest as I was discussing this with Will in the comment section :). Took the AI900 this week. In my opinion this was easier than for example AZ900. I read through the MS Learn path once, took the assessment test and then went back to the learning resources it told me I should freshen up on.
Took another practice assessment, watched about 75% of these videos:
This was probably overkill as you can pass the exam solely with the MS Learn and a good understanding of when to use what Azure AI resource and responsible AI. Passed with 889🥳
Short notice on my background: I have worked with AI solutions and have a background in Comp/Theoretical Chemistry so knowing the mathematical model to choose for ML was already given, but the questions do not go into depth and beyond the basics this was of very little help. More might be tested more in the higher level certifications.