Like you said, there is no single correct fingering for chromatic scales. Fingerings depend on the context of the music - dynamics, speed, what comes before and after the scale, articulation, what note you start and end on, etc. - not just the fact that it is a chromatic scale.
I don't understand what you mean when you say you use a different fingering every time. Does that mean you could use different fingerings in different pieces of music, or you use different fingerings for the same passages in the same pieces of music?
In general, I try to limit the crossovers and thumb-unders by using 4321 for right hand descending) and 1234
(for right hand ascending) as much as possible.
This approach is the most facile, and it is also sounds the most even, because you are using adjacent fingers as much as possible, as opposed to a 313131 approach, where you are using a relatively strong finger in a strong position alternated with the thumb in a weak position (crossed under the hand).
Having said that, the focus of chromatic scales should be on the overall sound. In rapid chromatic scales - like the beginning of Beethoven op13 - you should not hear individual notes. Instead you should hear an individual gesture that starts at one point and ends at another.