Carry it on. call the airline and tell them exactly what it is and why you want to carry on. They should be accommodating...
Don't know about the rules overseas, but a typical cymbal case would be both too heavy and too big to carry on a plane in Europe. Sometimes the airlines are lenient, sometimes they're not, but unless you only play 3-4 cymbals and nothing larger than a 14", you definitely run the risk of being stopped at the gate. If that happens, you'll have to check in your cymbals, and if you only have a softbag with you at that point, you're pretty much screwed.
Flight cases are probably the most secure way to travel, but they're also heavy as all hell and might cost you a fair bit extra to check in.
I've got a Humes & Berg Enduro case coming in a couple of days, and I'll be flight-testing it for a gig next weekend. The case came highly recommended, so I'm hoping it will be up to the task. My last case was not so sturdy, and some baggage handlers had obviously dropped it at some point. The cetnre rod was completely bent out of shape (had to physically bend it back just to get the cymbals out), and some of the cymbals were cracked around the hole. Not all cases are created equal, it seems, so make sure you get a good one.
edit: I assume that by "flight case" you meant the plywood kind with reinforced corners, which is what I referred to when saying they are very heavy.