The difference is in the virtual device options that you will have to use as proxies for the security system state. There are more choices if you have a Smartthings/Aeotec hub, but even if you don’t, there are ways to have an Alexa routine turn on a proxy device that smartthings can see.
Virtual Switches After Groovy FAQ
Looking at the Alexa routine as an “If trigger then action” structure, the if part is the same whether you have a hub or not for this particular use case. The action is the same structure, but the choice of devices that you have for this is different if you have a hub or you don’t.