If your use case is "I don't want to understand Xen", then fine, just use AWS and pick the newest instances, they're usually the best.
AWS does have some words about PV vs HVM here: http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/virtualiz...
But really, they don't say much and that's fine. If you just want to run stuff, you probably don't need to understand the deep details of Xen or PV drivers or whatever; the cpu speed, memory, and "disk io"/"cpu credits" they document quite well will be what matters significantly more.
If you are at the scale of netflix, then it does make sense to figure out an extra several percent disk performance.
> I would totally care more about replacing stuff if I knew ... instead of "I have no clue what if anything is different
They almost always have blog posts accompanying each new instance launch which roughly outline the performance improvements and reasons that instance type is cool vs previous ones, even if they don't go into the depth of virtualization differences so often (which again, usually doesn't matter! for nitro, the C5 blog did talk about the visualization stuff in depth https://aws.amazon.com/blogs/aws/now-available-compute-inten...)