When you climb a great deal, you can use, and abuse your gear. Nowadays I abuse less, I use my Sports ropes more, and I abuse them less. It's a definite function of age, but along with age comes, a lot of knowledge in my case. Many people, even some people who should know better, say a ropes is just a rope. This is fundamentally not true. First think about the ropes intended function, and then pick the rope, price is not the first consideration! Colour is not the first or second consideration!
What is the first consideration? First consideration of a rope should be that it can catch your fall with out imparting so much force that it hurts you. The rope is the cord that binds the climbing protection system together. So it must stretch, to absorb impact.
The diameter of my rope is one of the main things I look for. Why? Well, thin ropes which have their place, are more difficult to use in belay devices, and wear faster. I want a balance, you probably should think about this more than me, because you defiantly want your rope to last.
Thin ropes, are less drag thru gear, and if they are robust because of a good sheath might last a good while. But really you need to think about diameter, For me anything under 9.4 is a red point super effort job, and needs lots of care. 9. 5 mm is bang in the middle, over 9.5 is getting a bit heavy and a bit slow on the clips and a bit too much friction. At 9. 8 the rope should be able to take a lot of abuse, and at 10 mm will last for a very long time. How we climbed on 11 mm is a wonder and testament to how strong we were in our miss spent youth!
get a good middle mark if you can!
Please take care of your rope! The more care of your rope the more care it will take of you! Unwind it care fully, not in a rush, get rid of every bend in it from when you first buy it. Seriously the more care you first put in the better. Try to belay especially when lowering without putting a slow twist in the rope, its very easy to do this, so take care. When lowering try binders and chains make sure you are no unwittingly putting twists in the rope.
So Edelweiss 9.5 mm it is at the moment.
I love 80 meter ropes, why, its not because they are heavy (because they are) its because I know they are long, as in too long for most people to screw up. When choosing a rope, think diameter, think length, think low impact force, think good middle mark, think good treatment on all parts of the rope, think price, and colour last. Look after your rope, and don't lend it to anyone, keep your eye on it, treat it right.