There was a long thread about this earlier... basic result seems to be if you have big thighs, they're gonna stay big, maybe get bigger.
I've always been told that fewer reps with big weights makes for bulk; lots of reps with lighter weight makes for strength and tone and endurance. Translating to a bike that would mean staying out of the Mashing Gears.
I'm a big-legged person but cycling has made them shapely, not bulky. And that layer of body fat means that I don't look like a muscle dissection kit; unless I'm actively flexing 'em, the muscles aren't that well defined, so I don't *look* as strong as I am :-) So when I'm wearing sneakers and riding a hybrid... (ah, but TWO commuters went by me this morning... oh, my poor flailing pride!!! No, I am *still* going to stop at the stop signs, all the more fun when I pass you...)