I haven't switched.....but I'm Platinum at Marriott the past few years and have been diamond at Hilton for about a decade.

My personal preference is the Hilton program. For myself, breakfast EVERY day is a big difference. I really hate marriott's "resort" rules not giving you breakfast (especially when it seems 50% of the international hotels are resorts) and Marriott Hotels not giving breakfast on weekends. Also I've found too many Marriott lounges closed on the weekends for my taste.

I also like HGI and Hamptons much better than Courtyards (especially internationally where Courtyard Does not provide internet access unless you pay some stupid rate like 15 euros).

That said, Marriott has the travel package which gives you airmiles and a week hotel stay.

Beyond that its property specific. There are some Marriott properties I choose over Hilton - I choose the Brussels Renaissance over Brussels Hilton or Conrad because they have a nice gym. I choose Hilton Prague over marriott Prague because the Hilton lounge and the hotel gym are excellent. In Warsaw I like the Marriott location but Hilton property is better IMO. I could go on and on, but the main thing is being top tiered allows you to "try" more properties and decide.

Neither program is perfect. Hilton is my "first" choice in terms of the program but I choose more and more based on property. At one time I stayed at Hiltons no matter what - now I choose based on service and property specific things. If I were in your shoes I'd at least make the effort to be Hilton gold in addition to Marriott.