I have no experience with the iS 150 so I can't say for sure that it will equal the performance of the 147. I had a F147 too before the F160 that I now have and I liked the board(s) a lot.
With that said, I think the 147 will still plane a little earlier than the 150 because of its width in the tail in 7-10 knots (+ or - one knot difference??). Once on plane, the 150 has the potential to go a little faster, jibe better, but won't go upwind or deep downwind as well.
Formula 160; iSonic 111; HiFly Move 105; Tiga 263; '85 Mistral Superlight.
Maui Sails TR 11.0; 9.2; 8.4; 7.6; 6.6; Maui Sails Switch 6.0; 5.2; Maui Sails Global 4.5; 4.0.