[ebikelaw]

The very lightweight HTML Gmail lacks all of "normal" Gmail's latency-hiding features, which is one reason it uses so little memory. Gmail preloads all of the messages in the thread list so when you click them they are displayed instantly. HTML Gmail doesn't, and when you click a message it fetches the body from the origin. The tradeoff is yours to make. I find the HTML version infuriating when I'm tethered on mobile because every mouse click takes 10 seconds. On the same tether I can leave normal Gmail open all the time and it's fast. Ironically the lightweight Gmail is more usable on a fast, reliable wired connection.

[nine_k]

I think that the contents of the emails in a thread is a minor part of 150MiB taken by the full version. I suppose my entire inbox (the not-archived part) is much smaller that that.

[ebikelaw]

Indeed, it's not the data but the code to support it. There's a bazillion features in there designed to avoid the user having to do additional page loads. For example in my Gmail memory profile there's 20+ MB of code to support the real-time chat feature in the sidebar. You can argue about whether there should be a middle ground implementation that has the email preloading but not the real-time chat. Developer and project manager time is unfortunately finite.