Three different questions!
Baer is the most expensive, but certainly one of the "coolest" mods.
Wilwood is cheaper than Baer, but really are meant for the track (I know - I have them on my 67 and they need care and feeding).
SSBC is, in my opinion, probably the best choice for someone who wants a kit (unless you have bucks to throw at it, in which case, Baer would be a choice). The nice thing about SSBC is their soup-to-nuts type of kits (you may have a couple small items that you have to get, but nothing significant). They also have a long track record - back when I was first thinking about converting my 67 to discs they were around (that was in the early 80's and I still have their brochure!). They have several different flavors, from stock GT replacements to big brake kits that can hold up on the track.