Hmm...I think Opera would be faster in both cases. In my
experience, Firefox took up over hundreds MB of RAM after running
for a few hours with 10+ tabs on, but that wasn't the case for
Opera. Opera seems to limit itself to a certain amount of RAM
(below 150 at almost all times), no matter how many tabs (within a
reasonable number, obviously) were on or how long it has been
running for, without any noticable drop in performance.
And regarding tweaking, Opera does have a "opera:config" page for
users to change advanced settings.
Besides, Opera is the only mainstream web browser on the Windows
platform that passes the Acid2 test. For me, it is quite an
important feature as I often have to deal with CSS code (briefly,
CSS handles the alignment of elements in a web page) and having a
browser that can render CSS accurately would save me unnecessary
time on "debugging" code that wasn't even wrong in the first place.
And from there, I work on fixes for IE and FF based on the CSS code
that renders correctly in Opera.
But of course, Firefox has its strong points as well. For the first
part, FF renders CSS code correctly for 99% of the time. It has a
wide library of user-contributed addons, some which are useful for
web development (Tamper Data, Web Developer's Toolbar etc), and
some that make NSFW sites "legal" during work (credits to Adblock
Plus). And the upcoming FF3 (or Fx3, according to the official
abbreviation) is able to pass the Acid2 test as well. So, if FF3 is
more efficient in memory handling than its predecessor, I may
consider a switch in the future. But for now, Opera - FTW.
Well, the above points may be irrelevant to you at all. At the end
of the day, I guess it all boils down to what you are using the
browser for. If you are one who just surfs the net and enjoy
skinning your browser plus those "Today's Weather" add-ons, go with
the fox. But if you are a speed-hungry minimalist, get Opera on
your side. Nevertheless, our dear old IE is still usable if you
don't really spend much time on the web or you surf mainly IE-only
websites.
And that's - my 2 cents. =D
