Mario's place was ideal for our trip. You can't find a room closer to the Venice boardwalk! The bed was very comfortable, the apartment was very pleasant and hands down the best value for money if you're looking to spend the majority of your time hanging out and exploring Venice and Santa Monica.
I'll say as a warning (and I don't mean this disparagingly) you have to be okay with having absolutely no view and music blaring between 10am-8pm. When we arrived I worried the music would disrupt our sleeping, but the entire boardwalk is silent after a certain hour, and waking up to people talking, skateboarding and good music playing was just the energy we needed to start the day.
Mario was a great host, we didn't see him too much unfortunately but every interaction was very pleasant. I highly recommend Mario's place.