When I was choosing which hosting provider to move my website to (away from UK2net and WordPress), I came across these two website builders: Squarespace and Virb. Both are professionally made and designed, and to be able to chose between them I had to do some thorough research and find out about all of the features they offer.
Luckily, both providers offer a trial period of 10 (Virb) and 14 (SS) days, so you can build a website which will be available online even before you pay for the service (password-protected though).
There are about 20 templates to use on both platforms, but I, personally, find the Squarespace's ones more professionally looking.
Squarespace Themes has a lot more options to modify. For example, they have dozens of Google, typekit and standart websafe fonts, and allow you to modify margins, paddings etc with sliders or figures.
I thought that Virb gives you FTP access but that doesn't seem to be the case. Squarespace only gives this option to those who are subscribed to a developer's website. However, if you were to do that, you would need to start from scratch, in which case the themes (templates) wouldn't be available for you to use. So if you think your skills as a developer aren't strong enough, I wouldn't suggest choosing this.
If you have a website that was previously built on another platform (WordPress, Drupla, ModX, Joomla etc) and it had fast traffic from search engines and other external links, to be able to get visitors from the same links, you will need to maintain a similar directory structure. In other words, new links need to look identical to the old ones. Neither Virb nor Squarespace allow you to get the same directory structure you had before. But there is another way to keep those links working - URL mapping.
Virb doesn't offer this feature. Squarespace does. Simples!
Virb doesn't have an in-house e-commerce system, but you can easily integrate BigCart or Etsy. Squarespace offers e-commers when you sign-up for their Business plan, but it works for US, Canada and UK accounts only.
If using Virb, keep in mind that all of your blog posts will appear in full on the main blog page (there is not "excerpt field" when you enter a post); and that if your posts are long, the main blog page will take ages to download and the tedious scrolling will become annoying very soon. I didn't manage to try all of the themes, but the 3 that I did try could neither shorten the text in the blog posts list nor did they have a separate excerpt filed to insert an announce to a blog's article.
Also, I had a php code to show some statistics from istockphoto.com on my previous website but, unfortunately, I couldn't make it work on Squarespace because it includes some PHP codes.
Contact Us Form
Virb doesn't have a form editor which means that there is no integrated feature to add a "contact us" (or another) form to your website. Of course, alternatively, you can use a 3rd party solution (for example, WuFoo or Formstack).
Squarespace allows you to use 4 different types of form fields (Text, Text Area, Name and E-mail) on their Standart plan and up to 16 on Unlimited and Business plans.
The biggest issues with Virb (for me) and why Squarespace wins... for now
Virb's problems: Blog (no description/excerpt part), no URL mapping, no Contact Us form, no in-house e-commerce.
And.. to be honest, I like the Squarespace templates more :).
In my opinion, Virb is still a good decision if you are building a simple portfolio website and do not need much flexibility there (but why would you need FTP access then?...)