More important than the equipment issue is the question of how you are currently training. Do you have access to some good hills right now?

Long hills/big climbing days can strain your knees, your lower back and your hamstrings. I think the best way to prevent that is to build up to it in your training. Practice hills!

Personally I live in a very hilly location and I have a compact double on my bike. I have some great lower gears, not quiiiiiiite as low as a triple, but I don't like the awkward way triples shift, anyway.