To be honest sarah the french horn is probably harder than the other brass instruments, with the exception of trombone, as I am using the example of brass instruments! Now it HAS to be harder because the Harmonics are so close together!
Yes, I can see that is difficult - but all instruments have difficulties. As I have said, I have known people take to the French horn like ducks to water. Some people thrive where other people don't. It's easy to say, "Oh I can't play that because it's more difficult." It's more true to say it's because it's more difficult for you. (I suspect it would be difficult for me, too). French horn has great difficulty from the close harmonics, and also I believe hand stopping isn't exactly easy. But unlike the violin, you have four(?) keys which the hand stays on. You don't have insane position changing up the neck of the instrument like violinists and cellists do (and harmonics are close - so are notes on the violin especially in the high positions). A cellist at a high level has to be able to leap from a low position to a high position with incredible accuracy. He (or she) also has to keep the bow flowing, much, much harder than it looks, and know what to do when the hand arrives in the right position. He has to be able to do completely opposite things, in fact, with both hands - and it takes a surprising amount of stamina just to keep the arms in a position to do so. Totally, utterly different set of skills to the horn player. But I can't believe that the one is inherently more difficult than the other. And I am sure that all instruments, when it comes down to it, are difficult to play well. Some tend to be easier in the beginning, some are rock hard at the beginning and then get easier, some are a steady progression. None of them are easy to play well.
As I say, I know people who took even to the horn like a duck to water. I'm sure certain personality traits and even physical things make the difference from one person to the next - I imagine a fine sense of relative pitch is incredibly important on the horn as it is on strings. But to play well is not easy on any of them, and the differences are more about us than the instruments. You can say "oh the horn must be more difficult because of X", but if for one person the area of difficulty is not something they find difficult... It'd be like saying "singing must be easy because you don't have to control an external instrument". But I think anyone who says that needs their head examining - for me, at least, that makes it more difficult. For someone with arthritis in their finger joints it would be a different story.
