I've done 10 Rick tours and 10 Road Scholar programs (5 international).
Group: In my experience, many of the Rick travelers are a bit more independent than the Road Scholar tour members. I think having to get yourself to the starting point and having to manage your own bags weeds some needier travelers out. There is an expectation with Rick's tours that you'll need to be flexible since you have to sign the "No Grumps" policy. I think that makes a huge difference. Last year on a tour in Cornwall (!!!) we had a free night for dinner on our own. I had scoped out the restaurants for vegan options and knew where I wanted to go. I invited any of the solo travelers to join me. One of the other women was worried about walking around town (Falmouth) on our own and decided she would eat at the hotel (where we had eaten for all the nights) and tried to talk me in to joining her. I'd enjoyed the hotel food but really was ready for a change. She finally decided to come with me and another group member and seemed to enjoy herself. I find the Rick tour members tend to do more research on what they want to see in free time as well.
Food: I like not having all meals included on Rick's tours. Sometimes I just want gelato for dinner, hahaha! Some of the Road Scholar tours are now excluding some meals which I really like. Since I am vegan I've always gotten a vegan option on all of my Road Scholar tours. Never had Laurie Beth's experience but I am sure it will happen one of these days. I do touch base with the guide after the first meeting (both Rick and Road Scholar) to say I'm vegan and ask if they will let me know if there is a group meal that can't accommodate as I can forage on my own. So far, so good but I always have Clif bars or food in the room. I'll just add that I've had pretty good luck on the Rick tours getting vegan group meals as well.
Guides: I've been very happy with all of my Road Scholar guides except one for London back in 2013. I think everyone complained about him (very nice and knowledgeable but so incredibly dull - really torture to listen to him even on interesting subjects). Most of the guides I've had equalled my Rick guides. The guide I had for Brittany ranks at the top of my favorite guide list along with a couple of Rick's guides.
Itinerary: It's come down to me cheating on Rick with Road Scholar based solely on itinerary. Road Scholar runs a lot more programs but WAY fewer dates. They are also often more specific whereas Rick's are more generalist tours. For instance, next spring I'm doing Rick's Belgium and Holland tour as I particularly want to see the WWI battlefield and also Keukenhof. Next Fall, I'm doing the Road Scholar Art History of Belgium and Holland which is very focused on....uh....Art History (lol) of the Low Countries.
Gratuities: I've not had the experience of noticing people tipping the guides/drivers/local guides on Road Scholar tours. That would drive me nuts. There have been times that I have tipped the guides privately and discreetly if I know they've had to work to get me vegan options but I don't let anyone know I am doing that.
If you are doing Venice, Florence and Rome, you'll really only have 2 bus days as you transit from city to city. The longest bus days I've encountered were on Rick's 21 Best of Europe tour and frankly, I was glad to have a rest day. The guide also gave us language, culture and history lessons during bus time. Luggage transfer will only be a PIA in Venice. You'll be on a vaporetto with the group for the transfer from the hotel to the mainland and the bus. Everyone else will be doing it so you'll have company. You want to make sure you have your luggage packed as light as possible and that you only have 2 pieces - your suitcase and perhaps a day bag. Getting from the airport to the hotel is not really that hard. You'll know the stop to get off at and you can look at a googlemap ahead of time.