One disadvantage of producing your site through a large company is they won't have time to support you. This is why small web design companies have a more personal touch. WIX and Square Space are both hosted and support in America, they are in a different time zone to Australia. This is going to make speaking to a real person about your problem nearly impossible. They will simply respond to your support ticket with text. Then they will wait for your email response. This extends the support process by days at a time and can get very frustrating.
At shiny we will resound to your support calls with a few hours. We can even come to see you if you don't have time to leave the office.