As sophiegirl mentions, there are a number of questions that need to be answered to really answer your question. To add on to them....

How many nights a year will you be traveling? If you travel enough to get top elite status in multiple programs, that can be very helpful in making sure you get treated right in more locations (and it makes finding awards easier as you have multiple programs to search for availability.)

Do you have flexibility to use whatever CC you choose or must you use a company CC? Some programs, like SPG, are much more dependent on the CC to build up points. What is your flexibility with the type of hotel you can stay at? FS, mid-range, suite properties, long-term stay, etc? Some programs are more limited in their various properties than others.

How do you like to vacation? If you like to take 1 or day stays at locations and move around a lot while on vacation, then Marriott may not be as beneficial for you. Marriott's program is optimized for 7-day vacations. (Marriott has probably the best hotel program awards in their Travel Package awards which come with upto 120K airline FF miles and a 7-day hotel stay.) Other programs are better for shorter stays.

What type of benefits would you prefer for you elite status? Different programs focus on different benefits. If you are looking for regular suite upgrades, then Marriott is not the program for you. Marriott's strength is that at FS properties a Gold/Plat elite receives CL access (or breakfast) M-F no matter the rate (including award stays.) Though Marriott does exclude properties they designate a "resort". Their "elite guarantees" are probably better than any of the other programs as well. I would definitely suggest taking some time and reviewing posts/threads from each of the programs to see what each program's strengths and weaknesses are.

Basically, it gets down to what is important to you. You have to spend a lot of time in a particular chain's hotels to get the points and the elite status. And then you will stay in that hotel's properties again when you vacation. So making sure your stays are comfortable, enjoyable and get you the best vacation possibilities are what you need to be looking at. And what makes someone most comfortable, what is most enjoyable, and what will work best for someone's vacations is different for everyone.