Diono Rainier weighs 27.5 pounds which is a little less than Diono Radian that weighs 28.1 pounds. On the whole, both car seats are pretty bulky and heavy hence they’re equally difficult to transport around. We therefore don’t recommend them for users who may keep interchanging them back and forth on different vehicles.
When we look at seat dimensions, Diono Rainier measures 15.6” by 17.8” by 28.2”. When compared to Radian, the seat is wider on the top and narrow around the base. Therefore, it will most likely take a lot of space when used in small cars.
The dimensions of Diono Radian are 16.1” by 16.9” by 28.4”. This one is a little taller than Rainer but less wide on the top than Radian.
Overall, both of them are bulky even though they’re designed to fit three sets at the backseat. Fortunately, both car seats can be folded down when not in use. Like when you’re in a trip so packing is a breeze.
Diono Rainier wins again since the side walls are extra deep and thick providing additional side support to the child from sudden impact.