Sunny,
what ACD do you have in mind?
here are the basic reasons that I usually give my clients:
1. flexibility : ACD has a limited number of stats available to base the routing on. It also cannot (in most cases) connect to third party products.
2. stability: ACD is inherently more stable that Genesys; however, the stability comes at the price of limited functionality and extensive training by the staff. Usually, you do not want your SVs to touch PBX. With Genesys, you have an extra isolation layer between them and your PBX. So a good idea is to have ACD routing as a backup for Genesys routing
3. performance: ACD is fast. There is no question about. But, for high volume of calls, you are putting an enormous amount of load on a single machine. With Genesys, you can distribute the load to your heart content.
4. reporting: ACD reporting is very accurate. Genesys reporting is rather flacky. But, the deviation is on average under 2%. In exchanger for the 2% deviation, you get a rather stylish graphic representation of what goes on, instead of a VGA piechart with 14 dot System font. Also, you can base your routing on your historical figures, such as days of the week, months, number of agents and so on. With ACD you are limited to what they have in the drop down menu.
To summarize: ACD is simple but stable. ACD is a truck that will get you and your load from point A to point B in one piece, regardless of the pavement. Genesys is similar to a Ferrari (a red one). It won't run in the woods and eats up a lot of gas, but it sure helps you score.
If you are looking for stability and simlicity of use, go with ACD. If you are thinking about something over 200 agents and there is a chance of having a variable inbound workflow and fragmented workforce, choose Genesys.
Does it make sense?