No one can argue that the most important aspects of an infant car seat revolve around its designated function - to protect the baby from the rigors of the urban vehicular experience. This is key, and I won't compromise in this. But after safefy requirements are satisfied, there are many other things to consider: how heavy, how much room it takes up in car, cost, ease of installing in car, abillity to clamp onto a stroller, etc.
One other consideration: looks and style. Many of these seats are truly ugly, or at least they seem so, particularly to the fathers who are forced to use them. I am talking about calico prints, teddy bear patterns, gingham squares, frills, even leopard and zebra prints. I don't want to come off sounding like some kind of style elitist, and if someone can show me that my baby will truly enjoy the little flowered print (which his back is against anyway) I might repent, but at the moment I am unconvinced. Fortunately, some manufacturers have gotten the message, and have designed great seats with all the functions of a safe and effective device, but with looks that please. The Italian seat by Peg Perego, 2006 model, with Side Impact Protection comes to mind, and this is available in the U.S. The model pictured below though wins in the looks category, for me. By Maxi-Cosi, a Dutch company, this product is not for sale in the U.S. as they have not sought to submit their product for approval here. Sleek, simple, elegant, and meets European safety standards (which generally are more stringent than U.S. standards anyway. What a nice looking seat. This is the Cabrio in Black Reflection color: