Maxi-Cosi Baby Car Seats - pebble, pebble plus or Cabriofix?

sorry if this has be asked before...

i am really struggling to see the differences / benefits between the Maxi-Cosi Pebble, Pebble Plus and Cabriofix. having spoken to Mothercare, I am still none the wiser.

we have an iCandy Peach Pram (with adaptors), and have been gifted a Maxi-Cosi 2way Fix base.

help! I am so confused