I totally agree with Remi,
I have the 2012 UltraSonic.
As Remi suggests, it's wider than the Futura 141, so therefore it will plane in less wind and stay planing
in less wind.
If you get the US147, and a 9.0-9.5 rig, you will plane earlier (less wind needed) than anything but a full race formula board (also wider) but to get the earliest planing on the formula board you need even larger sails.
The US147 will plane earlier than the Futura 141 (narrower) on equal sail sizes.
With the US 147 you get earlier planing and good speed even in the lightest winds (windspeed in which you will still be sub-planing/slogging on the Futura 141.
The Futura 141 may have a little top speed advantage if you have enough wind, but you will be planing nicely on the US 147 in a knot or 2 less with the same sail size.
As Remi also suggests, the US 147 is a little more difficult to jibe (due to it's greater width) but you can
quickly adjust your technique so it jibes just as nicely as the Futura 141, just takes a little bit different