I would tell you that after using Fastmail, Gmail seems positively glacial and slow. Like, it's borderline "why would anyone put up with this, except maybe because they haven't used good email before". And we just got a huge fine for missing a bill here because a family Gmail account spam-binned it, which isn't an issue for my Fastmail, which handles spam better.
It could be a little faster, maybe, but with good indicators of things happening under the hood, which Google offers, reliable results, and the daily comparison to m365, I have no complaints.
And really, the only faster email setup I have ever used was mutt right on the MTA. I haven't used Fastmail but ProtonMail (my backup choice due to their combo mail+VPN+drive offer) certainly doesn't feel faster than Google.
My Fastmail account receives, at most, a handful of spam emails a week. And Fastmail uses a personal spam filter heavily weighted off your own mail and reported spam as opposed to the whole world's emails. Obviously it has weighting rules that are easily understandable and readable in the headers, but my own trained filter has a really strong impact on the spam score.
Whereas I find Gmail both often misclassifies legitimate mail as spam, and fails to catch obvious spam, the biggest issue is it rarely is fixable by my actions, because it's mostly based on Gmail-as-a-whole's perspective on spam. My Gmail is also receives an absolute deluge of junk even though I haven't used it as my primary mail since 2016. I have a somewhat short Gmail address and I strongly suspect it gets dictionary-spammed because the server name is a given, it also gets signed up to random things I never signed up for (including the NRA and Shutterstock, both of whom I had to contact and ask to remove me).
