I bought and chose LR3 reluctantly in its day because of its ability to do 99% of what I need internally. I had actually been using SilkyPix Pro (ver. 4 I think) and to a lesser extant RawTerapee at the time. I didn't need LR's library (I have a separate DAM software for that), but the spot healing and lens corrections were items I used to have to leave the other software to do in Photoshop. At that time no other RAW software offered that.
Price was also a factor. I had access to a student pricing of LR and then the pricing went down with the newer versions.
Finally, I got used to the workflow. Over time I've re-evaluated other RAW developers (I'm doing C1 right now even), but the workflow changes versus benefit haven't made the change appeal to me, yet. SilkyPix could win me over again if it was cheaper. C1 Pro may win me over, but it's workflow lacks the intuitiveness. I also find it is a bit lagging on my PC. I always keep RawTherapee because it is free, but it does lack features that have always kept it as a back up.
Anyway, I don't really go for brand. I want decent output and I want a relatively simple workflow. I do value my time, so at the moment the better output I see in my playing with C1 has to be significantly better for my time to justify the cost and time investment in learning to use it quickly and efficiently. Contrary to those that get hung up on favorites, I've found that I can get good results with almost any RAW software I try given the knowhow to use it. Most differences end up being marginal and time driven.