Advice on IIot Cloud services to use for a large company

Hi there!

Our client needs to start moving their data to some cloud services provider

All I've worked with so far is ThingSpeak, for smaller projects, but now this will be a large and continously growing project.

Client expects these abilities from the cloud system:

Hold a historic log that can be easily checked
Provides an easy to use graphical dashboard that allows the creation of panels
Can send an alert when thresholds are exceeded (sms/telegram/aown app...)
I know the usual AWS, Watson, Azure...but Ive never worked with them. I tried to experiment with AWS a couple years ago but it was a little confusing.
I know of other solutions like Thingworx, Carriots, etc

Can you provide your own experice with these and which one you would advice to use?

Thanks a lot!