It's currently easier to get Marriott Platinum or Gold given the SPG Reciprocity. What the combined program will look like is anyone's guess, though... but it looks like things are staying split through 2018, so there's still some value to be extracted via the reciprocity. I'm currently able to maintain Hilton Diamond, SPG Platinum, and Marriott Platinum (through SPG reciprocity) all with ~70 nights this year (and some strategic mattress hopping)... that wouldn't even make Marriott Platinum in that program alone.
For someone looking to maximize mid-tier status with minimal stays/nights, holding the Surpass/Ascend/Business card and getting SPG Gold on 10x 1-night stays would give you HHonors Gold, SPG Gold, and Marriott Gold all for $95 and 10 nights. This would be a great starting point for anyone just starting to travel for business late in the year, for example, especially if they had the SPG AMEX as well.