I am at the moment using 32 bit Palemoon 8.0 Portable.
The only reason I have not tried 64 bit is that I have not yet checked out whether my preferred Addons and Plugins are available for 64 bit.
I was on Firefox 9 and use the same extensions, but Firefox has become unstable and busted.
Some days Firefox cannot access Gmail unless I select the "basic" mode which is horrendous.
Consistently Palemoon is putting red squiggles under my typos - Even when I know better .
Firefox used to give squiggles but that stopped a month or two ago,
I guess some things get broken with progress,
but it is worse than disappointing that the last Firefox update never bothered to disable the Dictionary or even warn that it was not compatible
Both Firefox and Palemoon have the extension "British English Dictionary R1.19"