Presta Shop has an impressively simple look and feel. Of the carts reviewed it comes closest to a Web2.0 "out of the box" design and is pleasing to the eye with less clutter. It passes the W3C validator on the basic default installation. It has most all of the basic features you need and does an excellent job of providing an "easy to use" administration system. One major downside at this time is the minimal support for various payment gateways in the default install. Presta Shop has a modular design so it is possible to create a custom gateway to your vendor of choice.

Generally the tradition in most open source projects is that enhancements or plugins developed by the "community" are free. This appears to NOT be the case with Presta Shop, and one should be aware of this situation.

Zen Cart seems to have it all with respect to features. Unfortunately, it also comes across as more cluttered and busy. Though this can be controlled by changing the settings, this cart will require a lot more time to get past all of the features to your basic needs. Like Presta Shop and OpenCart it also passes the W3C validator on the basic default installation.This cart would be best if you need a lot of customization and need a maximum feature set.

Unlike Presta Shop, Zen Cart has a lot of free add-on modules that extend the default cart with features that might be needed for your business. This should be considered when choosing a cart.

Open Cart also has a nice uncluttered look and feel as well. It has a little less feeling of "space" but comes very close to Presta Shop. It supports more gateways and more Paypal solutions than Presta Shop. Like Presta Shop it also passes the W3C validator on the basic default installation. It is feature complete for most of your eCommerce needs. We would place it between Presta Shop and the Zen Cart on the number of features available.

OsCommerce is included mostly because it seems so popular. One of the major problems with OsCommerce is that it is structured using non-CSS techniques (Table based) which will limit one's ability to customize the cart without doing major template work. Unlike the first three carts, this cart does not pass the W3C validator on the basic install - 19 errors.

Like Zen Cart, OsCommerce seems to have every feature you can imagine plus a lot of add-in modules. In fact OsCommerce and Zen Cart are basicly clones of each other (my understanding is that Zen Cart is a fork in the OSCommerce project). The key exception is that Zen Cart changed from Table based structure to CSS based structure. The admin has the same basic structure and "look and feel" as well.