The other side of this is that there are less people at both Kellogg and Ross that want to go into IB, which is reflected by the percentages.
I attended the IB Breakout Session at the Kellogg Admitted Student's Weekend. From what I gathered, every top bank hires from Kellogg. People had internships from JPM, GS, CS, etc. in IBD. Also, there are fewer people gunning for interview spots so its somewhat easier to get the first round interview. If I chose this path, I don't think my options would be limited.
I think it is a similar thing for Ross. Almost all the banks recruit there, but there are simply fewer people interested. I saw campus interview slots for Lazard, CS, JPM, DB, etc.
So in the end, I think Kellogg would have slightly more cache by simply being a more reputed school, but both will offer several opportunities to break into IB. More banks hire more people from the finance schools, but there is also more competition for those slots.