I had to evaluate the big 3 for a company I worked at a few years ago. We were a G-Suite shop, so GCP was already in the running, but folks were also interested in the Office 365 option (We still used AD for local auth and had file servers etc, so not fully Chromebook style G-Suite), so I decided to start with Azure as it was the one I had the least experience with.

Long story short, on my first day I couldn't get the console to log me out, even after explicitly logging out, etc. I thought I was going crazy or just doing something wrong, but I absolutely could not get Azure to log me out. I had to create a support ticket and it turned into an incident. It was honestly all a bit ridiculous. I wasn't going to veto Azure purely on that, though it obviously was not going in Azure's favor, I did have to explain my experience and it was effectively banned based on that experience, because we were a small/medium business subject to HIPAA and more senior folks didn't like the idea of us going bankrupt due to HIPAA violations from our data getting exfiltrated.

It ended up being a pretty straight forward choice between GCP and AWS. GCP was already easy for us, because of G-Suite, but also our primary product encapsulated a TensorFlow CV ML model and TPU training was very appealing from both a cost and speed perspective.

Expensive and not at all startup friendly. Most startups are doing containers or serverless and Azure makes you pay for straying away from their PaaS business model.

Not to mention the way Azure handles networking and security is atrocious, bolted on to Active Directory.

I don't know GCP at all, but I do know that AWS Serverless is brain-dead simple to implement and very low-cost even when you begin to scale.

Not really startup friendly. Their market is almost exclusively the enterprise.

"Oh you have office365 and adfs? just move your monolithic enterprise java app to azure and save!"

personal opinion: absolute pain. everything is very complicated due to being connected to AAD and other services. lots of features but most of them useless. the legacy that they dragged along really is hindering.

Azure has amazing free benefits for startup. I formerly went through their Bizspark program which gave me a huge credit that let me have multiple VMs, relational database servers, etc for free FOR THREE YEARS.

I'm pretty tied to AWS at this point because that's who my employer uses but Azure was really great and their startup benefits were very generous.

https://startups.microsoft.com/en-us/

I don't know, but I've tried it briefly and it felt pretty dog. In terms of UI, ease of use, quality of software. I don't feel in general MSFT is as strong engineering-wise either. In terms of customer service, the first email you get from signing up is from an AI, so there's that.