That might be true for spiny lobster. I wouldn't know.
It's definitely NOT true for real lobster (you know, the ones with delicious claws). As those get bigger they just get tastier and not tougher. The meat-to-gunk ratio improves with increasing size as well. A 3-pound lobster has considerably more meat than 3 1-pounders. Of course, this presumes that you pick the arms and body and don't just eat the tail. Since the tail is the least delicious meat on a lobster, that shouldn't be a problem.
Around here, lobster often costs about the same per pound as hot dogs (though admittedly it has waste and hot dogs don't) so we tend to eat a fair amount. Larger ones usually cost more per pound for good reason. When they're priced equally we always go for bigger ones.