You may used or ever heard for these two analytics. I would give you some idea how different for these two products as following. It depends how your requirement and how much data that you need to get it from Analytics. Some website need just Usage information that GA is enough. But some large e-commerce websites, need to get more information about user behavior over purchasing process in complex user environment that may need to use Omniture.
1. It is free tool
2. It is integrated to Google Accounts that easier to manage
3. Easy to install and accessible to Google Adwords click data
1.GA does not have techical support. (Now they are starting the project Analytics specialists) that will cost to you based on each company will charge.
2. Delay of Data and
3. Tracking Goals (GA allow only 4 Tracking Goals)
4. Cookies : 30 Days
Let's compare with Omniture as following.
1. They have 24 Hours 5 Days Technical Support via Phone (Online Customer Support, Knowledge Base, Forum, On Demand Video Training, Details Manual, Regional Class and Certificate)
2. Custom Metrics (Allow up to 120 Metrics) to analyze
3. Omniture has 15 years cookie
4. Omniture can track more in Conversion, Variables and Events
5. First Cookie availability at Omniture
6. Advanced Feature in Segmentation (Demographic, Psychographic and Behavior)
1. The cost is very high. The cost is also based in traffic volume.
2. Need expertise to handle Analytics Analysis
3. Take time to implement the system and testing which take more than GA