Well lambda+API gateway is somehow what AWS is pushing in the serverless, scalable and pay per use app model, so for me it seems quite logical to compare. Cloud functions can't really compete feature set and integration wise in my opinion.
AWS's offering is more mature, but has a concomitantly steep learning curve; using something like serverless[1] can reduce the exposure to that, but there's a lot of stuff to learn to get things working nicely with AWS.
