I have used all the main ecommerce platforms. Here's my 2p worth
It does ultimately depend on what your requirements are - so check before you jump
Shopify - no thanks at all , expensive and there are better less expensive alternatives (some free)
Magento - the beast - so slow and cumbersome. dont jump on to this platform it will bog you down in techy issues from day 1
Prestashop - I do like this one - upside it does the easy things well. Product combinations etc. Downside - you host it yourself, so you do security, patches etc.
Woocommerce - need to be on wordpress and rather limiting.
EKM - liked the look but didnt suit the requirements of the project.
xcart - the fastest of them all. Covers all the bases and options. Mature code. Downside - you host yourself and do upgrades or pay someone (but that's the same with other platforms generally)
ecwid - my usual goto option. Easy to import existing products (in csv format), hosted in the amazon EC2 cloud (so updates/patches are done for you - phew) , you copy/paste 5 lines of text and wherever you do - your shop will appear. one shop - multiple websites. Killer for me though is it fits directly into facebook. Facebook ad to drive people who have an interest in your products direct to your product. It's also free at a base level and cheaper than shopify at other prices points.
I have also dabbled with open cart which seemed ok (but open source - which can be troubling)
Ive transferred plenty of shops into ecwid it's a fairly simple process. Once did 1500 products which worked smoothly - the caveat being they didnt have much complexity re upselling / cross selling, wholesale / retail price points. So there was a bit of a tidy up afterwards, But did that whilst the old shop still running. Then just switched over, including creation of all the user accounts etc.