I think you'll find most people will recommend Firefox over Opera, I certainly would myself. Firefox has excellent rendering and plugin capabilities, whereas Opera can have issues with some complex CSS/HTML rendering.
It is all down to personal preference, but for overall compatibility I'd suggest giving Firefox a go
Well, actually Opera comes out top on nearly all key points ...
It has proven to be the fastest, most Secure and most compatible, in conforming to standards it is the only browser that passes the Acid2 test, than either FF & IE inc IE7 but has the same/similar "compatibility" problems as FF
It was also the first with innovations such as Tabbed Browsing, was first to have Search feature, was first to have pop-up blocking .
Technically speaking Opera is better but like Muckshifter I tried it for a while and have been with Firefox since it was Firebird. Opera's GUI sucks big time too, imo.
thanks again. as i use firefox already i will stick with it as i have had absolutely no problems. one day i might try opera just to see what it`s like .