Roger is travelling at the moment and will probably get back to you soon. In the meantime, I'll offer my opinion and vote in favor of the Formula 175 and not the Hypersonic 105. But let me also say that there are better boards than either for a beginner, and which will be more user-friendly for you. If you have only these 2 to choose between, then get the Formula as long as it is in good condition.
As a self-described beginner, you will do better with the width and volume/floatation of the Formula board. It is a good board for light wind conditions, but usually powered best by a sail 7.0 or larger. As a novice, you may not be able to get the full performance that the board offers, but it will allow you to improve as it will be more forgiving than the Hypersonic. The Hypersonic is shorter, narrower and has less volume. It is also a board that needs good technique to sail. It likes to be fully powered and you have to be ready to go with it and control it. I would not suggest it as a board to learn on, unless you are waterstarting, and already planing and in the harness and footstraps.
hope this helps,