i rate a mono based on it's diameter. big game and izorline are incredibly tough, that's true- but they are thicker and break over their labeled strength. i remember reading somewhere that biggame 12lb broke at over 14lbs of load. the diameter is equal to 15lb of most premium line. so it really wouldn't qualify as a 12lb line, would it?
i'm fast becoming won over by pline as my first choice. it does seem to stand up quite well under all conditions and the diameter of most of their products is equal to or below that of the competition. the price is quite affordable for the majority of their offerings.
considering all the dough i've spent on rods, reels and lures, i have no problem forking over a few bucks extra on line. afterall, it's the only thing that connects me to the fish. there's a lot better areas to budget on first, IMO.