At the moment I am using Magento but i dont really like it becasue of the limited capabilities, for example: I want to create a printshop so people can choose multiple options like: paper thickness, paper quality(shinny effects) number of order(100,500,1.000,2.500 etc..) a inbox so they can describe the design that I will create an upload function, so they can upload there design or show examples I need too know which webshop is the best that allows al these functions. and that I can easily adjust the html,css, php scripts. webshop platform that I can choose from DantoCart FreeWebshop Joomla & Mijoshop Joomla & HikaShop Joomla & VirtueMart Magento OpenCart OsCommerce OsDate PrestaShop QuickCart TomatoCart WebsiteBaker & Bakery WordPress & e-Shop WordPress & Marketpress WordPress & WooCommerce WordPress & WP e-Commerce xt Commerce ZenCart
ZenCart is good for beginners, but if Magento is not enough for you, ZC probably won't be enough either. OsCommerce is often claimed as the most powerful set of options, so you may want to try it.
Last year i have similar project but for a classified where user can offer and upload the design and vendor or admin will review. Once they both agree, the user can then checkout. I was using a component called jclassifieds and jmarket multivendor for Joomla. I think they also have wordpress now but i've used only the Joomla version. And you can freely customize because it is opensouce. I did not even buy it coz I was using the free version and customized it from there, no need for update or help.
Sounds cool but I can only choose from the platforms above because they are the only one that support bank payment plugins from my country.
What payment do you use? I think they support also several system. In my case, i've got pgseguro. I think the best way is you survey which one has the closest feature from your requirements and which one cost less to achieve what you need, and less costly to maintain ofcourse if budget is your concern, if not i would go for woocommerce.
to be honest with you, i have several clients running eCommerce websites and all of them either pick "magento" and or "woocommerce". magento has a better CRM integration though