I play the green Tortex sharp since nearly 5 years. Beforehand, I used nylon plecs in various thicknesses, creating a more mellow guitar sound. In contrary, the Tortex have an open, high pinched sound. I think that's because of the plec's tip: sharp (as the name suggests), resembling an arrow.
The material is hard (harder than nylon, anyway) so it feels "precise" to play with it. For my hands (normal sized) the plec's size are nearly optimum. The only problem: since it doesn't has ribbings, they become slippery if thex come in contact with sweat (I use a knife or scissor to aplly my own ribbing ;) ).
So to say, a great plec for every day use, either you play "rythm" or melody. To me, it is not the perfect plectrum for nylon-acoustic or western guitars, but give it a try. Maybe you are surprised how many pressence your guitar could have.