It's a toss-up between OPI and China Glaze. Both last a good while and come in a variety of colors.

opi because it last along time before chipping.

Recently started using Essie and am loving it. Highly recommend it.

My top two (if I can ONLY pick two) are OPI and butter London. OPI because of the huge shade range and love love love when they have special collections (can't wait for Muppets!). Butter London because it's really good quality and don't have all the chemicals that the others have it. I'm also limited as to what polishes I can buy due to being in Canada and couldn't jump on the butter London bandwagon until I found out they sell them on www.ebeauty.ca (a Canadian makeup site), YAY!!

My top two brands in nail polish are  OPI & Essie.

www.opi.com

www.essie.com

I mostly get them from local shop, however they don't stock much of new colors then I will go to herstyle-shop to get them. www.herstyle-shop.com

if it's a color I'll only use once, the quality is generally pretty decent, especially for the price.

I don't live in the US, so I don't have access to many brands and colors/styles I would like to try. However, of the ones available, I like OPI and China Glaze a lot :D the colors are amazing and they last a lot; I am an art student so I usually get paint on them on day one, so maybe I'm not they best judge :P

OPI and Essie, but Sally Hansen Insta-Dri for when I'm fed up with waiting!

I just had my acrylic nails done today with bright green China Glaza and OPI purple crackle polish.  What a GREAT look.  I used to only use OPI, but I also like China Glaza because of the colors.