The best of Britax Safe-n-Sound convertible child car seats in the birth to 4 years range are the Graphene, Millenia and Platinum Pro.
All these 3 models are for child from birth to 4 years old. All three models have ISOFIX installation system and can carry a child in a rearward position up to 30 months.
These 3 models comes in the standard Thermo Bamboo fabric with various colours or you can get these model in the Nanotex fabric, which is currently only available in black. The thermo bamboo fabric is great for comfort and breath-ability, while the Tex also made with thermo bamboo fabric with Nanotex technology - meaning the Tex fabrics are water proof and stain proof.
We always get asked this question. What is the difference between the Graphene, Millenia and the Platinum Pro? In simple terms, best describe as small, medium and large! The size is a reference to the width of the convertible car seat. The Britax Graphene has a width of 44cm, while the Britax Millenia has width of 47cm and the Platinum Pro is 50cm in width. If you intend to fit 3 car seats across the back row, only the narrow base of the Graphene will fit in most cars. For families with 1 or 2 children, the Millenia or the Platinum Pro would be an easy fit in the car. If you car is wide, then you may still have space to fit an adult in the back seat. While the seat is in a rearward facing position, the specifications shows the Graphene requires 52cm distance between the back seat and the front seat, while the Millenia and Platinum Pro requires 60cm.
With regards to features between these model, the Millenia and the Platinum Pro has pretty much the same features. Both use the same frame with easy adjusting headrest and push button to release harness located at the front. The Graphene headrest adjustment is a bit harder to used when compare to the other 2 models and the release for the harness is different.
As for safety, the CREP safety rating as published on https://www.childcarseats.com.au indicates the Millenia and Platinum Pro both have high forwards safety of 4.6 stars out of 5. While the Graphene only score a CREP rating of 3 stars out of 5.
Which one should you buy? They are all very good quality child car seats with fantastic features, quality, comfort and safety. It depends on the size of you car, number of children's you plan to have and your budget.