Squarespace vs Wordpress
Why to choose Squarespace platform over Wordpress (or, why I've moved my website from Wordpress to Squarespace)? To make it short, I'd compare Squarespace to Apple while Wordpress is more similar to Android to me. So you pay a bit more for Squarespace but get a lot less headache.
Go for Squarespace - if you are not technical enough to support your website on your own and is not ready/do not want to pay someone else to do it.
Go for Wordpress - if you do not mind spending quite a lot of time updating, installing, re-installing, protecting, etc your website
Go for Squarespace - if you do not mind less flexibility but need a stability and if you do not want to worry about your website being safe.
Go for Wordpress - if you want to spend less money and get more for free. Wordpress has free ecommerce plugins! So if money is an issue - Wordpress is your choice. Squarespace will cost you a minimum of $10 a month. You can find a cheaper Wordpress hosting (about $5, not to mention promo prices) on the market.
If you are a developer - no questions asked - Wordpress is your choice, unless, again, you do not want to spend a lot of time supporting your website.
If you do not want to wake up in the morning to find out that half of your plugins are not working because of the latest Wordpress update - go for Squarespace. When and if they update anything - they are always there to make it as smooth as possible for you.
I personally haven't tried a lot of Wordpress hosting companies - just 2 - Media Temple and UK2. And I hated the support. They are rude, careless, and, as of Media Temple, just show you that your problems mean nothing to them. Especially if you didn't happen to read the small print (even if there was no small print). The best answer I got from UK2.net was (after I was waiting for their response for 2 weeks) - "We are sorry but we've been really busy".
Squarespace support is brilliant. Very polite, very helpful. They have a great Knowledge base, they have Forum, so you can find an answer in a matter of minutes and if not, they are there to help.
Choosing a Squarespace template for your website is not that easy though. It is not complicated - no, quite the opposite. It just takes a bit of time. What helps is that you can literally try all of them out and see which one works for you. In their knowledge base you can find all features explained.