I am buying 2 new half ropes for trad (TM, Cederberg, and Western Cape country routes) and am wondering whether to get 50 or 60 meter ropes. 60 meters seems like the trend and so I was planning to do that but then started thinking: Why pay for, firstly and secondly carry up, an extra 20 meters of rope, that will very seldom be used. To me it seems the advantages of 50 meters outweighs the disadvantages.

Advantages of 50 meter ropes:

cheaper
lighter to carry (most significant advantage when lugging gear up Yellowwood, Tafelberg or Towerkop)
faster to coil
quicker to pull through, after pitch or abseil

Disadvantages:

limits pitch length
limits abseil length

I very seldom do a pitch of longer than 50 meters, and don't particularly like to, due to almost inevitable rope drag, and the fact that on harder pitches I am likely to run out of rack before I run out of rope. If I really need to hurry on easier ground simul-climbing is probably a better option.
Also I know of very few abseils where having 60 meters is much of an advantage. Maybe off Africa Lunch, but I am pretty sure you can easily scramble the last part off 50 meter ropes; and maybe on down time at Yellowwood. Can't think of any others.

So it seems to me that going for the extra 10 meters reflects that "but I may need it one day" thinking that means you end up carrying something around just in case, seldom if ever use it, and would in fact be better served by not having it, due to the disadvantages you incur.

I suppose one possible advantage of 60 m is that if you damage and need to cut off a section close to the end, you still have long rope.

What are other's thoughts and experience on this?

Agreed on all the pros and cons, including the 60-advantage that you can chop a damaged rope.

Climbing established pitches in the established pitch-combinations, your deductions are correct.

As you get more and more confident, you will find that you do want to lead pitches of more than 47m (I say 47 because there's always some caught up in knots and stances etc)
This may not be in very easy territory where it is easy to communicate the need to simul-climb, but might be linking pitches, or finishing off a proper pitch by scrambling the extra 10m to the summit rather than needing a whole new pitch.

Ditto with abseiling on established descent lines at 'crags'
If you are wanting to experiment a bit more (country routes...) 60s can make it much easier to bail if you get in too deep. Reason being firstly there are less abseils, but more importantly, when bailing you need to find and stop at the last place where there is a tree / good place to make a bail-anchor. Lets say that there is probably a good bail-anchor to be found every 30m (which is perhaps optimistic) that means that the average abseil pitch on 50s will be 30m, and the average abseil pitch on 60s will be 60m.
It's a debatable point but that's my 2c.
Of course there are orang-utangs on the forum who have never had to bail - you can make your own decisions.

FYI: You might have read he article on Mayan who freed the Salathe wall on El Cap while we were there. She used an 80m in order to be able to move around the wall quickly...

Thanks, Ant. I agree totally with your points. Basically having 60 meters gives you more options, but what I am really probing is: How often does one really need those options. So, how often do the permutations of abseil (or pitch) length, whether established routes or not, really result in you saving an abseil or a pitch? Obviously your example with 30m works, but if the length was 35m (or almost any other amount, longer or shorter), there would actually be no difference in the total number of abseils you needed with either rope length, unless your are bailing a VERY long way, so that small advantages accumulate, but we are never that far off the ground in the Western Cape.

So I suspect it is very seldom in bailing that an extra 10 meters actually gives an advantage. (And maybe its more about that lurking fear of being suspended 10 meters off a ledge in the growing darkness, kicking yourself about having made a 50 m choice) So perhaps it is just about the peace of mind knowing that if a such a situation arose - you would have the options covered. But not covering all these options may save you lugging an extra 1kg around the hills for years, and the accumulated seconds of time saved coiling may be more significant in the long run.

The issue of being able to climb longer pitches is probably more important - but personally I dislike doing this, and also contend that one usually slows down towards the end of such a long pitch, due to rope drag, longer time placing gear including on stance because of less gear options, and communication hassles with belayer, so that stopping shorter and having an extra stance, may actually be quicker in the end.

If you're working the Salathe Wall I could see that a longer rope would be good. But that is pretty different to most of the climbing I do.

I'll throw a curve-ball.
The only time you really benefit is in the added rap-length. Snort and I discussed rope lengths once (either on the ledge or while opening the easy route on YW - if you haven't done it, its really good for the grade) and, if memory serves (it's not often we agree so I almost can't believe we did ), we deduced that to all intents and purposes a 40m rope is the best compromise. The irony here is that if you try do Snort's 'interesting' abseil on yellowood, you actually NEED thin 60's (they need to be thin so that they streeeetch).

I digress though.

A solution for the layman who cannot justify more than one set of ropes is a set of 60's. This way around you can use them together and enjoy 60+m raps, or if you not needing to rap that far, take one and climb on each end - that's a 30m pitch. Use slings in the anchor to not lose the 3m Ant refers to and you'll be surprised how much you can do.

Long ropes have far less advantages than short ropes. long raps often get you into trouble. 50m ropes are just fine.