Hello,
I won’t say it's tough to get a job through off-campus drives but when you sit for on-campus drive you have competition just with your college students that will be hardly 1k-3k but when you sit for off-campus drive you have competition with a much larger crowd that depends on the number of openings and region. The off-campus drive is open for all the colleges in the region.

If I talk about value of campus placement over off-campus placement You get to be recruited by your college. They will ensure that you get the job 110% and also the offer letter on the said day. They will ensure the security of the working place and the environment too. You may not expect a large package but it is a good option anytime. Off-campus is not bad , but what if you are there for an interview and they got their candidate very early , so you might be asked to leave.

Hope this helps you.