It depends on your interests. Both JEE and NEET are difficult examinations. Around 10 lakhs students apply for these examinations each year and only around 10k students are selected, which makes cracking these examinations extremely difficult.
If you are interested in Physics, Mathematics, and Chemistry, JEE will be better for you. But if you are more interested in Biology, then you should choose NEET.
MBBS studies are way more difficult and hectic than NEET. MBBS has a vast syllabus with 19 subjects to cover in 4 years. NEET UG, on the other hand, is a competitive exam but NCERT books and coaching would be sufficient for it.
After entering into MBBS, every day will be a test and you need to be the best among the lot for a good career. Every time you need to reread, revise & update yourself with recent advancements. The peer pressure in any medical college is very intense.
During NEET preparation, you will have many people to guide and mentor you. This is definitely not an option in MBBS.