What should be my first IWC?

I want to get a watch to celebrate heading to uni, I really love the look of IWC pilots but I know very little about watches. I want to get the mark XVIII as with the sellita movement inside it is more easily serviceable and I want this watch to be something I have for the rest of my life. Is that a good idea or should I just save for the mark XX. And how does a watch like that stack up to say the omega rail master with its caliber 8080 which you can get for cheaper then both the XVIII and XX. Any advice would be greatly appreciated.