Personally I would look at creating a main category page and then have the services in pages below that allowing you to fully optimise each of these services. Having separate pages means you will be able to optimise all the on-page factors specifically for each service strengthening the chances of ranking for more of your services as key factors such as the page title, h1 header and other on-page content will have the specific service keyword in them. Don't forget to make sure your meta description is also specific and has a good call to action in order to help encourage the all important click-throughs from the search engine results. Also make sure your URL is optimised to contain the relevant service/service related keyword. As you say you need to create unique content for each. Having separate pages in your internal link structure allows you so much more freedom to optimise for the specific services based around relevant keyword research for each. I would also consider how you could possibly earn relevant links to these pages as this will also help increase their authority and ultimately ranking.
You might find having a look at this useful - http://moz.com/learn/seo/internal-link
Hope this helps!