I did both for GCSE and enjoyed them equally. However, it is important to note:
1) Latin is often considered prestigious and probably beneficial to have on a uni application ahead in the future, but German, as a modern foreign language, will open up far more doors for you in terms of usefulness and employability.
2) Latin is useful for learning the roots of language and helped me with my Spanish gcse (I took Latin, German and spanish for gcse and now do spanish a level) BUT you need to be dedicated to the literature side
3) Along the line, if you do a language for A Level, it's far more useful ro have German as a facilitating subject and one that boosts your employability too. Unis would generally prefer it too - look at their list of facilitating subjects. However if you enjoy Latin and succeed in it, defo take it further!
4) For Latin I got two separate gcses, one in language and one in literature, whereas German I got one. This might influence you ro take Latin ro get two gcses maybe? Idk!
5) not gonna lie, Latin could get very tedious and I got and a* in language but scraped a low B in literature because I hated the poets lol
6) German you have to do listening and speaking whereas Latin exams are all passive - just translating and comprehension. What suits you best?
8) whatever you choose, be aware if you want to do the other one for a level you most likely can't (ie you can't do Latin gcse and then German a level as you don't have the grounding)
7) finally at the end of the day choose what you feel you'll do best at xx