Kellogg is a great school, but I'm not really sure I agree with the argument that it is head and shoulders above Darden for recruiting. Kellogg places more people at M/B/B because the class size is twice as big. I also would say that Kellogg and Darden's alumni networks are similarly strong (as our career services). Both schools are quite similar culturally in that students generally have great experiences and as such are very active alumni. Again, Kellogg has more alumni but on a person for person basis both groups are very strong.
Upon acceptance, I spoke with a Darden second year who has an offer from McKinsey (in Chicago no less) and she said the school recruited very well at M/B/B this year.
Go to Kellogg if you think it's the best fit, but there is no way Kellogg is worth $100k more than Darden based on job prospects. As has been said Darden is solidly a top 15 school (and top 10 according to some). Kellogg likewise is a top 10 school (and top 5 according to some). I'm not sure the difference this far up the ladder (when one school involved is not Harvard or Stanford) means much.
I would also note that as has been said a degree from a top school does not guarantee anything. Look at the law school bubble to see that.
Plus It's not like a company looks at every Kellogg student before moving onto Darden. If you are good enough to get a final round interview from M/B/B you will be on equal ground with other candidates. The big difference may be that more K students get these final round interviews, but of course there also are more people applying for these spots.
I personally have an admit from Darden with a half ride and am wait listed 3 other places. It will be a tough choice for me at all these places if I get in off a wait list (and with a full ride the choice would be a lot simpler).
In either case I think your choice is K vs Darden. I wouldn't even consider Duke at this point (of course I prefered Darden to Duke from day 1).