I'm a big advocate of managed ecommerce platforms for standard smaller stores [i.e. you're not doing anything out of the box so why would you need the cardboard die-cut]... they're not as flexible but the upfront work required to get to a sellable state is far lower, changes rollout to you, hosting is managed through to site uptime not just server uptime,.
All this means that you're able to spend your money on UI, photography and copy rather than installs & development. Tempting as it is to use one of the major open source platforms you really need a better reason than it's free or it's customizable to take that route. Selling is not about cutting corners and as mature as ecommerce is getting, shoppers are increasingly wary of the small-business looking style.
Lots of options too... BigCommerce, Shopify, CS Cart [hosted], Volusion, etc.
As for which to pick you'll want to look at styling & customizing options, built in features that you'll use, plugins to your merchant, plugins to your product inventory, plugins to your accounting and of course price.
But that's just my $0.02