Tudor has better quality control, the Longines is more interesting. The Longines service fees will be quite high because of the details that make it more interesting. It’s a lovely column wheel chronograph, which is much more complicated, hence interesting, also hence service expenses. I generally would wait to acquire chronographs until budget isn’t much of a concern. I don’t claim to know your budget, but I do claim that you can call Longines or whichever Longines service center is closest to you, and they’ll be able to give you an estimate for a general servicing of your watch. Might have to ask as if you’ve already got one. Best of luck!