I can't comment on anything for GCP but I can offer some advice on the AWS front - Basically, there's a lot to learn/setup.
I've taken 2 courses for AWS and there is still an lot of their services I don't know about. You could probably setup an EC2, install PHP7, MySQL etc and get along quite nicely but you'd be missing out on the features AWS has to offer (Multi AZ, Auto-Scaling, high availability, RDS failover etc).
I think it would come down to your budget for hosting if you were to go to AWS, it's extremely scalable so you'd never outgrow the solution that's setup (If done correctly) and even if you have a low budget there are plenty of cost optimisations you can do to lower costs (Reserving instances instead of using on-demand for example) but if you're only wanting to spend £50-100/month on hosting then it may not be for you as a full AWS setup would probably cost in the region of £500+/month (Easily) It depends on which features you'd like, it could quite easily be £1,000+/month.
Was originally going to do this post as a comment as I can't offer a full comparison to GCP (or any info on it for that matter) but I ran out of space in the comment field. If anything I'll need to look into GCP now. Hope the above helps!