Hi Joestrip, Glad to see you made it here (I'm the person on Fodors who pointed you here). Of the 2 choices, I'd recommend staying 4 nights at the Courtyard. Granted, it is not in an ideal siteseeing location but it is closer than the Marriott Park Hotel. And, you wouldn't lose any time in changing hotels midway through. As I mentioned on Fodors, there is an hourly shuttle to Ottaviano St. Peter's metro stop (but be there early as it can fill up and you're stuck for another hour). And there is a nearby train station. If you have the points and if it is available, I'd recommend the Grand Flora, a much better location for siteseeing. Do a search here on 'Rome' for forum entries that others have posted. Have a wonderful trip! And, by the way, I apologize for the state of mess that this Insider's site is in currently. Apparently, Marriott recently contracted with a new vendor to host the site and they have made a terrible mess of it and went 'live' long before it was fully tested.
I just stayed 4 nights at Courtyard Central Park, and it was a great experience. Their shuttle is inexpensive and convenient, even though it only runs hourly. You can easily walk to the train station (but generally have to change from the train to the subway - but not a big deal). The staff was great, service was excellent. I'd encourage you to read others comments on Marriott Park. You will not find many people with anything posotive to say. You can't go wrong with Courtyard Central Park. I go to Rome frequently and had no complaints.
Depends on how many points you want to use. The Flora is a much better and convenient location but if you don't mind bus rides then the Courtyard is just fine. The Flora has a rooftop lounge for breakfast and drinks and can save you lots of food money and the view is very nice. Not sure but they might still be running the stay 4 nights and get the 5th night free. So if they are, and you can stay 5 nights in Rome, you should only stay at one property.