FF138 will probably plane earlier..... US 147 will probably have better speed once planing.
96 wide trumps 93.2 in the early planing dept.... 93.2 and the more modern tail shape/cutaways
trumps the additional width once you are planing.
If you decide get the US147, let me know.
I've been looking for a FF138 since I let mine go several years ago.
I have the US147 and it planes really early, but not as early as the FF-138 if I remember correctly.