I find myself in a minority on this one, but a big part of why I switched to FastMail is Gmail's search was always slow and typically insufficient for me. E.g., Gmail didn't (doesn't?) do stemming, meaning I needed to memorize exact phrases to find messages. I've had no such problems with FastMail search and it's remarkably quick.
I had the same experience years ago. Checking again today on my GMail account shows that partial string searches (or prefixes) don't work at all, but I don't really notice it because it gives good search suggestions in the popup.
For example, if I search for a partial string, say the first part of my last name, GMail finds no messages. But there are hundreds of messages from my family members with the same last name in my inbox.
Another example: searching for Verizo results in "no messages found", but GMail recommends I search for Verizon and that shows all the messages I expect (at a glance.)
Gmail search definitely stems. I just spot checked a few irregular plurals and their singular forms are all found. One other benefit of Gmail search is it also searches Docs and other private data. For some reason the Gmail search is more effective and faster than Google Docs' own search.
It's been a few years since I've actively used it. If they added the feature, fantastic. I recall looking for an email containing "dog" and search for "dogs" and couldn't get a match.
It's unlikely I'll be switching back soon, if for no other reason than I'm prepaid on FastMail, but how is searching over large accounts now? I found with more than a few GB of email, search would take upwards of 20s. I had to get very aggressive about deleting messages to keep the search time down.
20 seconds is completely outside of my experience. You were searching with the gmail frontend, or via IMAP? I have 5GB in Gmail and I get instant results as I type in the search box, and full results in about one second when I hit the enter key. I only have a little bit of email in my fastmail account so I can't really compare it.
This was with the Gmail front-end. It's entirely possible there was just something messed up with my account. I haven't come across too many others that have had similar issues, but most people I know have much smaller accounts.
Thanks for letting me know my info is out-of-date. The problem with these sorts of comparisons is it's hard to use both options extensively, simultaneously.