Chris,

Standard RG-6 will work just fine. Quad shield is going to cost more plus you have to use Quad connectors. I have done many hook-ups using Standard RG-6. In fact, in some instances, I have used the exisiting RG-59, which is not near as good as RG-6, and it worked just fine.
As for digital signal on coax, it has to do with bandwidth. RG-6 will carry a larger bandwith than RG-59.
Quad shield, will reject more interference than RG-6.
The newer style compression connectors are weather proof also. You need a special tool for them.
And they cost more. I can get standard connectors for about 20 cents each. Now you can also get moisture resistant and weather proof. 1 style has just an "O" ring in the end and the other has the "O" ring and is flooded with silicone.
As to JC's answer, Better cable better performance. Cable WILL and does go bad, and you may get signal thru it, but it can be bad. If cable sits in water for a period of time, the water will get into the cable and the shielding will corrode and break the ground. Also, little critters do a fine job of eating it sometimes.
Is any of this cable getting buried? If so, you need to get direct bury cable. It is flooded with silicone, and it is nasty stuff!
If you have any questions, just ask.