If you are hoping to move up quickly, I would suggest getting a Marriott Bonvoy Brilliant Credit Card to give you 15 elite night credits on your journey towards Platinum or Titanium. The Annual Fee is high, but essentially pays for itself, especially in the first year or two. A few months ago it even came with the offer of Platinum Status, I'm not sure if it still does or not.
Have you asked Marriott if they will match your status or offer you a status challenge? You might be able to leverage your Diamond plus a credit card to quickly get you to Titanium.
I find the sweet spot of Hilton Honors to be Gold. I find I am treated very well, get breakfast, etc. I don't find earning Hilton Points a worthwhile venture given the high number of points you need to redeem.
I find Hyatt to be the best program in terms of value of points, and upgrade options. That said, I find their program to be less enjoyable for lower end elites, which is really difficult since you cannot status match. You might find it too much of a drudge to work your way back up with Hyatt over the next few months, compared to the treatment you can already receive with Hilton.
If you are staying in Detroit proper, Marriott definitely has the market cornered for the best properties (Book Cadillac, RenCen, David Whitney, Metropolitan). In Las Vegas, Marriott has amazing properties on the strip (ie Cosmopolitan), and solid properties nearby. Hyatt also has great properties in Las Vegas (ie Aria, Bellaggio with MGM partnership).