Hi Talli,
A good technical argument would be, OACS has lower hardware needs. That is why OACS appeals to smaller organization that is tight on a budget. You can say outright there, take this desktop machine of yours. And lets install OACS. You can develop, use it for live site. Take the same machine and it will hardly be usable for .net both in serving for the live site and development. So in .net you need to buy your live server and development workstations. But then hardware is cheap this days... so not a real $ saver. Just a perception.
You can take the argument further. By saying that lets get all the junk PC in your inventory and make them into a cluster. To serve that kind of traffic .net will need X amount of hardware.
Another is inverse the argument of .net. As I have stated above, .net is easier because it has VS.net. You can say, .net needs a IDE to develop, so its harder. So additional cost in purchasing the tool. While in OACS a text editor is all you need. Then give them a very short demo and get their hands dirty on a template. Show them how easy to use the template or even ad_page_contract. Or even a very simple ad_form. Although such functionality can be done in .net, you will need VS .net to ease the pain.
You can also show them that .net's web form are generated from a DLL that MS ships. This would mean its not technically possible to alter it. Unlike in OACS the forms source code are all there. Its with templating's form builder and given to the developer in easier fashion in ad_form.
Still with all the argument that you can come up, Al is 100%. It will depend on the business context. You are unlikely to walk out from a MS shop with a signed contract. Also it maybe likely possible, that all your arguments will be subconsciously telling them that they are dumb in deciding to invest in MS. :)
