Low-quality paper or no paper - which is better for an undergraduate in PhD admission?
If the quality of the work is low, the student should neither publish it in a lower tier conference nor publish it as a technical report.  They should either make the time to improve it or toss it in the trash.  A bad publication, no matter what venue it's published in, is worse than no publication at all.

Similarly, a "publication" listed in a CV or described in a statement of purpose that isn't retrievable via google (unlike most technical reports, which are googlable) is also worse than no publication at all, because we can't tell if the applicant is lying.  (Sadly, some applicants are lying.)