Let's compare them now.
Biggest noticeable difference between the two booster seats is going to be aesthetics, as the back of the B2-Fix is primarily going to be plastic vs the back of the Solution Z-Fix has a more finished look like the Cloud Q infant seats.
When you lift the headrest of the Z-fix, the shoulder or side-impact protection also expands outward to allow for more room.
The Z-FIX does not allow for a cup holder to be attached in the US. The B2 FIX will include 2
The B2-fix can accommodate children up to 120 lbs, and the Z-Fix goes to 110lbs
The Solution Z-Fix is a more luxurious booster seat, priced at $229.95 while the B2-fix is a simplified version, priced at $149.95.