It might be an awareness issue. A2 has had a startup scene longer than Detroit. I was in QL's Bizdom accelerator in 2008-09, and there was no VC or startup scene to speak of. UMich has been spinning out tech startups regularly for a decade. The two ecosystems exist siloed from each other, but I think Detroit is a better choice since A2 startups can flock there and there is a faster growing community from what I can tell.
If you worked at a start up in Detroit, you were defacto a part of the Gilbert Mafia. I don't say that disparagingly, Dan Gilbert crew have done great things for the city, but its a one shop town.
A2 lacks a Dan Gilbert to make all the things happen, but it has a much more vibrant, Bay-like share-and-share alike, encouraging, open start-up culture.
Plug for A2-NewTech, a start-up meetup I'm a huge fan of (I'm not affiliated, just a fan)
The fastest growing tech startup in the Midwest in 2013 and 2014 was and is in A2 (Duo Security). We have multiple Google Ventures, True Ventures, Resonant Venture, etc. startups. We have the Tech Brewery, A2 New Tech, SPARK, Tech Arb, etc.
Barracuda Networks was started here. Google's Michigan office is here. One of the top 5 public universities in the world is all around us.
I can't imagine why anyone on HN would drive from Ann Arbor to Detroit for work when there are much better and higher paying prospects right here in A2.
I was living in the Detroit suburbs at the time, to be honest the team I was working with was amazing enough that I'd gladly do the drive to work with them again.
Though, I'm surprised they aren't coming to Ann Arbor- the real startup hub of Michigan.