Two different examinations cannot be compared. Both are set in their own way by the own faculty. I'll just say VITEEE exam is just taken to get admissions into the VIT college whereas JEE is an ALL INDIA level entrance examinations whose papers are set by different IITS each year. And the competition is really high in the second one. So as per my personal opinion and experience, JEE is much tougheer than all the other exams..
Kindly refer to the website below to know more about the JEE examination...
Also check this out, cracking the JEE examination can be easy using this.
Best wishes. thank-you.
VITEEE is a university level entrance exam without negative marks, while the JEE Mains is a National Level exam so the level of toughness will be more for JEE Mains exam. So if you have prepared for JEE Mains properly then you can crack all the other exams. So you should definitely appear for the VITEEE exam also. Prepare well for JEE Mains and practice previous years papers for JEE and VITEEE, and you will be able to score well.
For VITEEE you can refer to the below shared link to know the important topics and books to follow:
For JEE Mains, please refer to the below given links: