can anyone give me some insight on what we will gain/lose using REST vs extdirect?

since we are building a public facing webservice does that pretty much exclude using extdirect?

below is the actual question i need to answer but don't have enough knowledge to do so...

Theadvantage of a simple REST api is that anyone that can talk HTTP can pull datafrom the product. Its almost a builtin SDK. Does using Ext.Direct on theserver side mean that all clients are going to be required to using Ext.Js?