Yes, the context is global but it is architectural decision, and we need just one honestly speaking.
In general I agree, embedding wrapper around gecko is too fragile, and it works (starts) slower (due to the overhead). It renders fast of course, but settings pages aren't supposed to be that complex to requires super-fast browsers.
The only concern I have around the webkit is that it is abandoned, all major players switched to other engines, even QT themselves are moving elsewhere cutting ties little by little with it.
So on jolla we have out-of-the-box only WebKit (part of QT 5.2) and Gecko-embedlite (part of sailfish-browser). Everything else would require static linking or external dependency.
Gecko is modern, it supports HTML5 and all the bells and whistles, while webkit is old plain html4.1