If you are going to be averaging 14 nights per month, you will have enough nights to garner the highest level (based on nights) in both Bonvoy and HHonors. Bonvoy has Ambassador level, but that requires $20k in spend during a calendar year plus 100 nights. If you are allowed to book upgraded rooms, you might be able to get there. Average $200/night is the simple math.

My suggestion would be to get Bonvoy Titanium (75 nights), and decide if you like the treatment you get from that. From there, either stick with Bonvoy to get Ambassador (marginal benefits, especially given the length of your stays), or move on to HHonors and get Diamond there.

HHonors is unique in that you can get Diamond from a $450 annual fee credit card. If you are willing to get the Amex Hilton Aspire card, you can shortcut everything and get Diamond before you even start your stays.

Hilton and Marriott will have pretty similar footprints, everywhere you stay should have something in each family nearby. It is worth researching to make sure though.