I just tried the Labella after using the fender black nylons and found they are different beast.
The laBellas have a smother coat which feels nicer on the fingers. The Labellas E and A strings are a good bit larger than the fenders with the D and G strings being the same.
Unfortunately for me the tension of the Labellas are much greater than the fenders. I like my strings to me kinda loose.
The fenders have a much more "rubbery" or " snappy" type of sound to them IMO. I ended up using the E and A strings from the fender set and the D and G strings from the Labella set.
The D and G strings from the Fender set are too loose IMO and dont sound as good.
Overall I would say the Labellas are a higher quality string overall but just didn't suit my likes and needs (well at least 2 of the 4 strings didn't)
