Fast and not so good compare: http://www.ecommercespot.com/compare/nopCommerce-and-VirtoCommerce.aspx
Nop features what Virto dosent have are, Newsletters, Affiliates program and Loyalty program.
What i looked, nopCommerce have more extensions and more clear structure. Virto Commerce have some extensions and im not sure what are "COMMERCE CORE MODULE" etc. in apps marketplace, so do the virto commerce need many app to get basic ecommerce features?
And what comes to development, Nop has more freelancer available on upwork then Virto Commerce. When i searched both, i found only 2 freelancer with skill "Virto Commerce" and many many more with "NopCommerce".