There is no rope that does every job. Therefore when building your selection of climbing ropes here are a few points to consider.
As an alpine climber I keep quite 5 main ropes or pairs of ropes in my collection for regular use.
These ropes are made up of Tendon Master & Tendon Lowe ropes.
Summer trad and alpine climbing ropes
2 x 50m 8.9mm single Tendon Master ropes. I prefer the a thicker style half /skinny single rope for regular summer cragging and alpine routes. Often you don’t need to rappel longer than 50m. Therefore pulling up extra rope at belays, loading your pack with longer ropes when you rarely climb full 60m rock pitches is usually a waste. 50m ropes are quite cheap. Another bonus for tight arsed climbers. Having two single ropes for climbs where you have high abraisian and regular use i.e climbing granite rock routes is excellent as they ropes last allot longer than skinner half ropes. There is also the benefit that should one of your ropes get cut due to rock fall you still have a fully rated single rope for ascending / descending. In places like Chamonix many of the routes are set for 50m rappels as most of the local guides use this length of rope when working. They are also excellent for travelling i.e overseas rock trips where bag space is at a premium.
Summer / Winter light weight mission with 30m rappels
A single 8.9mm 60m Tendon Master rope. When long rappels are not necessary and im wanting to move light and fast on a big route, I take a skinny single. I prefer the single rope over a half rope as it allows me to lead harder terrain with confidence. A skinny single rope vs a half rope also offers extra confidence when simu climbing using locking devices such as tiblocs. I also keep a 30m 8.9mm single rope for ridges and routes where I plan to solo and just want a rope in the pack encase of an emergency.
Expedition climbing & winter ice / alpine climbing
When expedition climbing or winter water ice / alpine climbing where long pitches are common and rappel descents are made faster with longer ropes I usually choose 2 x 60m 8.4mm Tendon Lowe ropes. These ropes have the bonus of being both durable and light. Personally im not a fan of going longer than 60m with my half ropes. I feel the extra length is usually un necessary for both climbing and rappelling. In the mountains I am reluctant to rappel longer than 60m due to the likelihood of getting your rope stuck when pulling them after a rappel. I also usually find that if the terrain is easy enough to allow for climbing a 70m pitch then you probably should be simu climbing. The Tendon Lowe range of ropes have the bonus of a thicker size but the benefit of weighing the same as a much skinner half rope. They are therefore ideal for expedition climbing where the extra rope size makes them more durable but light enough to not slow you down on long approaches.
I also keep 2 x 7.8mm Tendon Master ropes in my winter rope collection. These are great for reducing weight in your pack when skiing into routes (especially when you ski as badly as i do). Often as in summer 2 x 50m ropes are all you need and I find the handling / dry treatment of the Tendon Master rope range some of the best I have ever used.
Lastly for sport climbing I stick with a 80m 9.7mm Tendon Lowe single rope. 80m seems to be the most practical length for modern sport climbs. Even though in NZ there are not many 40m pitches. If you plan to travel to Australia , Europe or America this is the right length to take. Personally for sport climbing I prefer to go with a thicker rope rather than a thin skinny single. This is due to thicker ropes being easier for your belayer to catch a fall with and the extra width adds to the durability of the rope. This is particularly important if you want your everyday rope to last more than a few months. There is no need to pay for dry treatment or other added rope treatments for your sport climbing rope. Personally I would go for price and durability over anything else when it comes to a rope that is to be used at your local sport crag.