Removed since allthecode change his question

From my experience, usually it is harder to create a hard and interesting problem.

When you are solving some problem on the contest, you know, that it is solvable (sometimes there are problems, that are not solvable in 2/5/etc hours, but it doesn't happen often), and you try to apply all of your skills that can help there.

When you create some problem in your mind, at first, you are not sure that it has acceptable solution at all, and you don't even know, where to look for the solution. But if you solve it, it gives you more pleasure. Some problems can remain unsolved for months.

Of course, I don't take into account hard only in implementation problems — they are rather for differentiate top participants than for solving for enjoyment.

Do you mean the difficulty between create a hard task and solve that certain task you created for other people during the contest? If so, I have some experiences.

There are different ways to create problem:

One way is finding some problem from anything (e.g. reallife tasks, games, or some math structs) then try to solve it. If we use this way, then create a hard problem is no less harder than solve one: because finally you need to solve it like what you do in the contest.

Like izban said, sometimes it is much harder to solve it when you find a problem yourself than face it in the contest. For example, I have tried to solve BrightLamps (250p of TCO2014 3A)　before it is used in contest. It is a variation of this task created by me: Ciel and Flipboard (Task D of Codeforces Round 190). I have tried it for hours but somehow can't solve it. But during the contest I solved it in about 20 minutes just because I know it is 250p.

Another way is to build a task by an idea of solution. I rarely use it, one of the task I designed in this way is this: PRIMEDST, I want to create something using tree-decompose and FFT and then build this task. So before I create it, I already know the solution. In this case, solving is much more easy than creating for myself, but can be much more hard to contestants. (It sometimes like a riddle)