If you are focusing on getting elite status (for elite benefits) at multiple programs, then attaining and maintaining top status in at least one program is probably better than mid-tier status in two programs.

If your focus is on getting some points in more than one program so that you have more award flexibility, then there may be some merit there, but I wouldn't jeapordize my top level status in a program for that. There is usually too much time invested in attaining that top level to then not get the benefit of it.

Now with that said, you might still be able to get top level with both programs. I don't know your travel patterns, but if you travel for 5 or so nights at a time (i.e. travel for a business week at a time.) You could have your first night out at the Hilton, then move to the Marriott for the rest of the stay (or possibly back to the Hilton for the last night.) Switching hotels within a trip, while a bit more of a pain, could allow you to get those 28 stays with Hilton and still get your 75 nights with Marriott. (Of course if you have the Marriott Preimer Visa card, then you would only need 60 nights.) So with as few as 88 nights it is possible to have top elite status in both programs and even have bit of points in both for awards.