There are several manufacturers of magnetic and optic crossfaders. However there are some really good standard crossfaders also.
It depends a great deal what you want to do with your controller if you need a highend crossfader. If you are hugely into scratching and have mastered the scratching basics (aka already have the level of mastery flutters, back squeegees etc.) then of course a good crossfader will pay off.
If you are more of a blend or controllerist DJ and only use the crossfader to enhance blends and cross grading, then a “normal” good quality crossfader (like the ones you find in all medium to highend class controllers) will be enough for sure.
.
