I looked at the site you mentioned and the differences between their recommendation and mine has more to do with your level of commitment in equipment and money than what would be best for you on the water.
As a novice / intermediate improves their skills, and if they are committed to the sport, he/she will continually add sails, masts, booms, boards, fins, etc. to cover a wider range of conditions.
After 26 years of windsurfing, and because of where I sail, I have a lot of equipment to cover every wind and water possibility. I have raced for all of those 26 years and wanted to have the perfect sized sail for every possible condition. I also have friends that sail with me that have much less experience and only have two boards and 3 or 4 sails. At their level of development, 3 or 4 sails is just fine. In 5-10 years, they may have 6-8 sails.
My recommendation for the "second solution" assumes that you are committed to windsurfing and either have or are willing to buy the necessary equipment (sails, masts, booms).
The negative side of having a lot of sails is trying to decide which one to use. If you only have a few sail options that cover a broad range of wind, it's easy to pick the best one, although it may not be perfect for the conditions.
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.