I was planning on getting the cheaper Aria, yeah.
It's fine to me if they don't snap in. I almost never use the carseat and stroller combo together. I always either pick up the baby and put them in the stroller or, in the early weeks, wear them in a sling.
what I found on this site reviewing the Aria was:
|Retractable car seat anchors that instantly attach to matching car seat * 55 lb. Weight Capacity * Universal adapter strap attaches to other manufacturer's car seats * 5-point security harness * Front bumper with child's tray opens/removes for easy access to baby * Removable, hand washable upholstery * Multi-position backrest * New, energetic color scheme includes three colors instead of two * JPMA safety certification * Designed in Italy * Colors include: Toffee, Rubino, Anice, and Ambra * Car Seat Compatibility: Most major models including Peg Perego Primo Viaggio, Peg Perego Primo Viaggio SIP|