I tried some of the ecommerce CMS ( prestashop, Hikashop, VIrtuemart and Magento) and in my opinion all of them have pros and cons.
The decision should be made keeping in mind some tricky factors such like how importants are :
configurable products
interface with the managment software (SAP,NAV, or propietary software)
If you have in-stock products or work with the "dropshipping"
and finally the total cost of ownership ( hosting,extensions,customization and so on)
If you have few products made by yourself , to go with a Magento website is a crazy thing!
Even a good Joomla+Virtuemart ecommerce could fit the bill.
But if you need a professional webstore with a lot ( 1000 or more) products then I belive that Magento is the perfect choice
Beside this, if you are a "forward-looking" person just like me and prefer to start directly with magento even with few products , be very careful, because is really a pain in the neck....
Of course it is possible to go with Magento on a good shared host , but performance are a lot worse than a VPS.
Also, for the same functionality you pay more than 100% in price for the extensions/templates and plugins.
Another important thing to remember are the maintenance planning ( database cleaning and patching) and the core updates....
To upgrade a Virtuemart store is a pretty easy task, but to upgare a Magento website is a bloodbath, and freelancers could ask you more than 300€ for a simple upgrade from 1.9.2.2 to 1.9.2.4
Never trust who tells you that if you do it in a test environment then you can rest assured that everything works well in the production environment.
This never NEVER-NEVER happens to me. It's always a cross-finger operation, and every time I pray for good. belive me.
It's the best Ecommerce , but it is like a F1 Ferrari:
Beautiful, with plenty of power , fast as lightspeed....but a nonsense if you must travel in a city full of traffic.
just my humble opinion.