Learn either AWS or Google cloud.  There is a lot to learn in either to become an expert. It makes sense to learn only one and both of them are top-notch. I am not fond of Azure or Oracle so do not recommend anyone to use either. 

Amazon AWS is superior to IBM public for several reasons.  The most important reason is the diversity of software tools, the geographic diversity and availability, lower operating costs and excellent customer service. All cloud companies are simply playing catch-up to AWS. 

AWS is definitely best of breed. All three major cloud providers are very close though.  So you really need to assess the features, costs, geographical availability, of each cloud provider and see which one suits your needs best. There are subtle differences in each so users…