After dropping my last crystal file I was on the prowl for another one today, trying to decide between another Essie and a Nailtek. I searched the product reviews and this board for a comparison and did not find one, so I am posting this comparison in case it helps anyone in the future.
Since I had Essie and Revlon in the past, I coughed up a little more for the Nailtek, and I am glad I did! Here's the skinny:
1) Revlon - not worth your $$. Too rough at first, then takes way too many passes to file anyway, nails on chalkboard effect all the time, dulls quickly. Just go for a better one IMO.
2) Essie - very good, this was my first one. However, after a year or two of use it dulled. The case was also a pain to handle and not lose the cap, which is why I ended up breaking it.
3) Nailtek - my favorite!!! It is smooth but has enough grit to file quickly. Once in a blue moon you do get the nails in the chalkboard effect, but just it's really just once in a while and the same is true with the Essie. Within a minute I learned to adjust my angle and motion without issues. A couple passes go a long way (but not in a bad way). This is the smoothest and most effective of all, plus the case is cute and effective. Now if it lasts the Nailtek will definitely be my HG!!!
I hope this helps someone out there. Crystal files are DEFINITELY the way to go if you want to grow your nails. I can't believe Trade Secrets charges $22 for the Essie, though. It's $9.99 at Ulta, and the Nailtek is $16.50 there too. Of course if you can get a coupon then you save a little more.