The big benefits - lounge access, EEO free second weekends, and free internet are available to both Plat/Gold.
Marriott has few suites, so little upgrade potential. I have had to change room several times when my Plat room was not satisfactory. Extra points for Plat is nice and 48-hour guarantee is nice - but it is not always available for a Plat.
I am trying to book a hotel next May and no Plat rooms available.
I think Gold is almost as good as Plat.