*sigh* first world problems.

I'll start by saying Johnson and Ross are peer schools and it comes down to regions. For instance, I have some friends at Johnson who want to go back to the midwest, so they had to do some off-campus recruiting to get there. That said, Johnson is giving you a scholarship of some sort vs. zero from Ross. I'd say all things being equal, take the $$, unless of course the idea of living in Ann Arbor is much more appealing to you and you want a different student life experience. Big Ten school like Michigan is going to be VERY different from Cornell.
That said, if you do get the Park Fellowship, you can try to leverage it with Ross to see if they'll throw any $$ your way to compliment the situation.
Now - if you get the Park and then get off Kellogg's WL, I'd say the Park Fellowship is tough to ignore. However, if you're interested in consulting, Kellogg is a beast in that department, and if you're looking at a $20K/year scholarship, I'd head to Kellogg esp. if you're interested in MBB.
The latest numbers from Kellogg are pretty impressive for the class of 2013:
McKinsey: 46
Bain: 38
BCG: 34
I don't know the exact numbers, but I'm pretty sure at Johnson the combined MBB hires are less than 10.