Hello Aspirant
You can prepare for a competitive exam in any language that you prefer. After the advent of NEP, it has allowed students and aspirants to appear for exams in either English or Hindi or any regional language.
If you are comfortable in Hindi, prepare in Hindi or if you're comfortable in English, go for it.
If you're asking from the perspective of scoring, there's no difference, everyone scores on the basis of their intellect, language has no role in it.

But if I speak from my perspective, I would advise you to do it in English because this is a world where English speaking individuals are preferred for a job position, their speaking skills are tested. If you can and have the passion to work on your language skills, go for English.
But keep in mind, this should not affect your preparation and your marks because you devoted time in learning a language instead of actually preparing for the paper

Hope this helps