What exactly is a mini-site? A mini-site will target a very specific keyword. So for example, if you are selling flowers, you can build New-York-Flowers.com, Miami-Flowers.com and so on. This will allow you to target that specific market much easier. Yes, it will take time to build the domain authority, but it’s much easier to reach the top of Google with very specific and highly optimized domains.
What is an authority site? Going with the same example, lets look at Flowers.com. You can build up a highly authoritative domain under Flowers.com and will probably get near the top of Google for many search terms that are involved with the term flowers. This is assuming you do one heck of a job with the on-site and off-site marketing.
An authority site will provide greater credibility with its visitors, while a mini-site will be seen as more of a sales type site. When we build mini-sites, they are usually one or two page sites that are designed to create a lead or push traffic to the corporate site.
Everyone should have an authoritative domain for their company and there are many cases where mini-sites will come in handy. Do not think that you will buy Miami-Flowers.com and boom, you are #1 on Google. There is still a good amount of work that needs to be done to get there.
Whatever strategy you choose, should be chosen day 1. Reason is, no matter which direction you go in will take months to build. Last thing you want to do is go down the wrong road and waste time and money.