We have stayed at Paris and Bally's numerous times.
Paris: We have stayed in the Red rooms, which are the renovated rooms on floors 26 and up. We have also had the end corner room which was awesome, but the furthest from the elevator. We have also had a regular room. No complaints about any of them. Paris has a number of dining options. Their "coffee Shp" the Ile de St. Louis is good; we also like Mon Ami Gabi for breakfast or lunch. the Eiffel Tower has a nice lunch/brunch menu that won't empty your wallet, but still give you a fine dining experience; the fast food option on the cobblestone walkway is decent in a pinch.
Ball's: the rooms in the Jubilee Tower are renovated and awesome. The drawback is that the entire front of Bally's is under contruction. This might not be too much of an issue. Dining options are the Sidewalk Cafe (coffe shop) which is pretty good. We enjoed the Calif. Club sandwich, which can easily be shared. I am not very fond of the Tequila Bar food; the Burger Brasserie is just a short walk down the cobblestone walkway and is closer to Bally's than Paris; they have good burgers. The steakhouse is closed for renovations. There are also some food outlets, like Johnny Rockets and Sbarro, on the lower level.
The monorail is not that bad, but it depends on where you want to go. It is NOT conveniet to Wynn, Encore, or Palazzo. Plis, if you need to use the elevators, good luck. From past experience, the one at Harrah's was particularly disgustig.
It is about a ten dollar cab ride from the MGM area to Paris and the same from Paris to Wynn. It all depends on traffic.
We have never stayed at Harrah's, so I can't help you there
Enjoy your trip.
Joy