Hi Takasar,
For an off-cycle internship the application process and competition are completely different than for summer internships.
Banks put a great deal of work into their summer programs as these usually include several rotations, group projects, organised meetings with senior management etc...It's usually considered the "royal way" of getting into IB.
Off-cycle internships are usually focused on one role or desk thus whether your profile/CV is attractive in the eyes of the revelant team will have a much bigger impact on whether you get invited for an interview.
Competition wise it is indeed easier as an off-cycle 6 months placement does not fit in most students' academic year. The application process is also easier as it usually just involves a CV and Cover Letter.
I landed an off-cycle at BNP Paribas after having failed to get a place on the graduate scheme following my masters so believe me when I say that these are a great way to break into the industry. I was the only one being interviewed for this role I believe.
I hope this helps.
J Cohen
Founder of IBMentor.com