[vinw]

Protonmail have a free plan, whereas Fastmail only has a 30 day trial.

But at the $5/month level Fastmail appear to be much better value (30GB vs 5GB storage, support multiple custom domains vs single domain, 600 alias addresses vs only 5 at protonmail).

I also like what fastmail are doing with JMAP.

As they're both free for at least 30 days try them both out?

edit: fastmail also has good notes integration with iOS if that's of interest