Good sails comes for 2 factors. Firstly you need a skilful designer and someone providing constructive feed back that the designer can interpret to improve the design.

You really need to know who is developing the sails and who is providing the feedback. The best feedback is from the designer themselves if they sail the class at a high level. They then know, first hand, what is working and what is not.

Probably the most important thing to ask is, dose the designer understand how the whole rig works together? integrating the sail into the rig as a whole is something that takes time and experiance.

Remember 80% of a boats performance comes from the rig...