I have a choice between a 60M 9.6 single, or a pair of 8.6 doubles, also 60M. Will be doing moderate classics up to 5.7.
Do we need the doubles for rappels, etc. Or is a Single fine?

Depending upon what your objectives are, you may need to make full, double rope rappels to get off efficiently and safely. Getting off of Bugaboo Spire, I was personally very happy with the system we used - a skinny single 60 m line and a 7mm, static tag line. We may not have found the easiest descent route though. The tag line came in handy when my partner and I scrambled the West Ridge of Pigeon Spire. We used to make a couple of raps on the descent.

Always best to run with doubles in the Canadian Rockies or British Columbia backcountry, unless of course your objectives are set in stone, then you can plan ahead. I always advise doubles vs a single and tag line as well, in remote climbing areas, for obvious reasons and flexibility. If you do chose to take a single, you need to take a 70m. If a rap has been retrofitted away from doubles in the last couple years, we usually set it up for a 70. I don't even own a single 60 anymore. Many doubles typically weigh the same as a single and make for easier hauling amongst partners. Doubles are by far the safer option for those who are familiar with how to utilize them correctly. Good Luck and enjoy.

FWIW, I quit using tag lines a few years ago in favor of doubles for safety reasons and because it is a boss system for teams of three. (I use rather beefy doubles).

I have to agree with the two replies above. although The downside is, you and your PARTNER need to be dialed in with rope managment. Dealing with 120 meters of rope, when your 1000' in the air, on a 6' ledge,cold and time and weather are of essence. A single and a small tag line for rappelling is a good option. Have fun the Bugs are awesome!

Thanks...