A 12inch woofer has more extension than a 10inch woofer. It can hit lower and play louder before the distortion numbers creep into audible levels. That's a matter of physics, there is no getting around it. Given the same level of woofer extention, a 12inch woofer can move a LOT more air than a 10inch woofer.
Yamaha has made some really cheap consumer grade speakers. I auditiond them a while ago, and I was not impressed. But the higher grade Yamaha subs are a good value. I owned one (not this particular model) and I liked what I heard.
Yamaha has made some revolutionary speakers in its time. I don't remember the exact model number. But Yamaha made the first speaker using berrylium tweeters. That speaker and its later incarnations were the de facto standard in audio reproduction in many recording studios throughout the world. Even today, after over 20 years, used speakers of that vintage still sell for over $1,000.
And Yamaha has made some revolutionary amp/preamps as well. The mx-10000/cx-10000 combo and its associated components were widely considered to be the best stereo components ever made. And even today, used pieces still routinely sell for over $8,000, that is if you are lucky enough to find one for sale.
