Both work as advertised. I have new one in the box for $130 plus shipping. Be very cautious about dead weight. If your boat swamps, the dead weight will take it to the bottom while the water filled weight will be neutrally bouyant. A couple hundred pounds for trim is fine, more than that you are taking a risk you should consider.
I do suggest that you put a towel down before you sit on it. It is more comfortable.
The Fat Seat has an 1,100 lbs capacity. You may need a 250 lbs bag for the bow to get the wake exactly the way you want it. Personal preference, of course. email@example.com