I changed to Refectocil originally because they do a better range of colours. I have a client who gets really blond brows, but has quite mousey hair and he (yes, he!) felt very self conscious about it. He had had a diaster in the past when someone had left brown on too long and he ended up with really dark brows, but we now use the light brown and it's perfect for him.
I also use the chestnut and red for my red/strawberry blond clients as brown or brown/grey mix just aren't always right for them.
Yes, I had used a couple of cheaper brands and they are fine for your standard range of colours. But once I'd tried Refectocil, I couldn't go back! Their colours take better and last longer IMO (not such a good thing if you want to see your clients more often!! lol)