Roger will jump in soon and give you some good advice, probably similar to mine.
There is never one simple answer. One thing that will help is knowing how dedicated and agressive you will be toward windsurfing. If you like to push yourself and are committed to making windsurfing a big thing for you, then I would suggest the Futura. If you are easy going and just like to have a little fun from time to time, then the Go may be the best for you. The Go is more durable and heavier. The Futura is lighter and a little more prone to damage, but is more performance oriented. Both are great boards, but if you are the first type of sailor I mentioned above, then the Futura will be more fun over the long haul.
However, I think the 133 may be better suited for your level of sailing rather than the 144. It will cover a broader range of wind conditions, especially in the 15-25 range. In fact, it is a bit large for those conditions (the 111 and 122 are better suited for 15-25). In fact, the 101 would probably be the board of choice in 15-25 winds for most intermediate and advanced sailors weighing 83kg. Advanced to expert sailors would choose the 93 or 101 in those winds.
The 144 is too larger for 15-25 winds and neither the 144 or 133 will do much in 6-10 knots. Both will just slog along. On the other hand the 144 could get up on plane in 10 knots with a 9.5 sail with some pumping. My guess is that with your own gear, you will head to the windy spot as much as possible and won't go out in 6-10 knots unless that's the best you can find.
Another question is how soon would you consider buying another board? If it is soon, you could go with the 144 now and add the 111 or 122 soon. If you go with the 133 now, you could add the 101 or 111 later. If you will be on one board for the next couple of years, then the 133 may be your best overall answer.
However, if you frequently get the 15-25 winds, the 133 will be too big most of the time. I know all of this is confusing, but there a lot of variables that surround board choices.
Give us some additional details about your commitment, frequency of sailing, frequency of 15 -25 winds and maybe this will help a little more with some additional suggestions.
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.