BBA

Hi Jeet, this will vary from person to person. What may be best for me may not be best for you. However these are the top BBA specializations
https://www.shiksha.com/bba/articles/top-specialisations-in-bba-blogId-12924

Both the courses have different perspective. If you want to get only to into the management and administration side of it then BBA in Aviation is better. And if you want to work in the finance, taxation, and accountancy sectors of the aviation industry then go for B.Com Aviation. The two countries you mentioned have limited job prospects for international students especially UK. They do not give work permits easily and prefer local candidates only. You must aim for an MBA and gain some work experience if you want to work abroad.

NDIM, Delhi is old and premier institution.
You can go for BBA.
Check last few year placements.

You are eligible to seek admission in BBA, BMS, BBE, etc. after 12th without arts stream and then go for MBA .