It depends on how much vetting the recruiter is doing and what their relationship is with the company.
If they are just coming in "off the street" and saying "here's a person I haven't worked with before, and haven't tested, whose resume seems to match", then as a hiring manager the additional 20%-ish fee they want is a big negative. I would prefer a direct applicant in that case.
If a recruiter I have already engaged comes to me and says "here's a person, we have already vetted them and done technical testing and checked their references," then I now have a candidate that has passed a number of quality checks and I'm happy to pay the 20% to hire more quickly.
Obviously there's wiggle room between the two (up to and including them just lying about having vetted you), but those are the ends of the spectrum.
I am currently doing this exact exercise - I have a position posted on job boards and have retained a recruiter looking for candidates for a 20% cut. The recruiter promises me they'll be presenting me candidates with references from their network, and will perform technical testing, and will find me a replacement if in the first 90 days we determine the hire is a dud. I make sure and challenge the recruiter on what they've done on each candidate to ensure they're adding value. In the meantime, I go through the ~100 resumes from the job board and cull out the 90% that are pure junk. Ideally from one of those two paths, people suitable for the gig emerge.
The third option though, a random recruiter I have not engaged and haven't worked with before cold-contacts me saying "here's a resume," I will generally ignore them unless the resume, or the spiel from the recruiter, really (and I mean really) jumps out at me.
So ask what their relationship is with the company and what they need to know about you. That will shine a light on whether the company will perceive them as adding value or not.