As long as it hasn't been in any accidents and is still in good condition then I would take the second hand one. The maxi cosi is a good car seat. You do have to check though because I know some car seats actually have an 'expiry date', this is usually about 5 or 6 years after manufacture. They say the first car seats can be used up to 9 months but in reality a lot of babies will fit in longer than this, it's the weight limit you need to take more notice of rather than age. My DS was in his maxi cosi until about 15 months. You should keep them in the first seat as long as possible as rear facing is much safer xxx