Pros: Easy application, nice color
Cons: Fades quickly; if you have long/thick hair, you might need two bottles
I've been dyeing my hair for about ten years, and I've tried a lot of different colors and brands. L' Oreal Preference is by far my favourite of the brands I've tried. The colours turn out great, the applicator bottle is well-designed, and you can never underestimate the importance of a good pair of gloves! The hair color by itself leaves hair feeling good, but the conditioner that comes with each bottle is amazing!
If you're deciding between two shades, you might want to go with the lighter one, as this brand tends to run dark. Lightest Auburn is a big jump from a strawberry blonde, for example.
I have very light blonde hair that takes color well. I usually dye it every three to four weeks, but I found while using this color that the roots faded quickly, making my hair look like it was growing out way sooner than usual. Part of this is probably owing to the fact that reds fade sooner than other colours, but I ultimately switched to a shade darker (Light as opposed to Lightest) and haven't had the same problem since.
I also have very thick hair (thick strands and a lot of it), and after it gets past shoulder length, I have to use two bottles to get it all covered. One bottle is good for a root touch-up (the root touch-up product wasn't nearly enough even for my roots), but since it's a red and the color tends to fade, it will look best if you dye it all over every time.