You can go either way actually. The single saddle will be much cheaper, of course.
If you decide to replace the entire bridge lemme suggest
TONE PROS Locking Bridge and Tailpiece studs. I have them on both of my Les Pauls and they're great. The biggest advantage is the increased sustain and tone, because the bridge and tailpiece are coupled better to the guitar. The other advantage is if you ever take all the strings off the guitar, the bridge and tailpiece stay put. There's absolutely NO ALTERATIONS done to the guitar. They retro right on. You'll have to replace the studs on the bridge and tailpiece, but NOT the bushings. The studs will fit into the existing bushings. I could tell the difference right away. And if you top wrap, the tailpiece is fixed to the studs better and won't rock foreward like a standard tailpiece. It also keep the intonation better as the bridge won't rock or move at all.
I ordered directly from them and thier customer service is outstanding. I believe they even make a lightweight version too if you're into going for the "50s" sound. They come in nickel, chrome, black, or gold. Once on the guitar, you cannot tell the difference in appearance or feel. Check em out... it's definately a big improvement, and if you need to replace anyway, this is the best choice.
Mike
~Vocals are what you stick in between guitar solo's~