The current UX for text zooming is pretty bad I do have to say. It's a feature that is really hidden and not well known. THere definitely need to be improvements to this.
Turns out that the page tweaks text zoom is different from View->Make Text Smaller
page tweaks zoom persists between changing tabs, reloads, and applies to all websites on the same domain.
OTOH, View->Make Text Smaller only applies temporarily, and it gets reset when you switch tabs. it also only applies to the current tab.
I've updated my previous comment to show the differences
I believe only Safari offers zooming in the text.