Hi Iso,
and welcome to the forum!
The numerous "personal opinions" is what makes the forum so interesting and informative. Like anything else, sift through the replies (mine included) and learn to apply the information as it applies to "you".
My opinion on sails concerns budget and use. "Generally" speaking....If you "don't race all that much" and "are concerned about expense", you may find that you are in the Dacron/Dacron end of the spectrum. If you "race a lot" and "expense is of no concern", you would probably be in the Mylar/Mylar end of the spectrum. If you "don't race a lot" and "expense is of no concern", you too can play at the Mylar/Mylar end of that curve. To make things even more interesting.....there are upper and lower ends; both in the Dacron and in the Mylar materials. Some Dacron cloth is "very nice" and some Mylar is "not so nice".

If you can afford the Mylars, then as another poster mentioned, have the sail built by someone that knows what they are doing.

I sail an awful lot, race in local distance races in the Gulf, and have been very satisfied with the Mylar (Pentex) Main & Jib designed and built by Randy Smyth.

In addition to the information you gather on the forum, talk to sailors that have your type of boat, sail in your particular area,
and maybe get to get on different boats set ups.

Hope this hasn't been confusing..I didn't intend it, id it was.

My input.
Dave