Please use the simple http service based approach is your application if is simple and it dont require the notification to the other clients when some operations are dont by the one client.
And go for the Blaze Ds if your application is very close to the Real time system and you wants the any acctivity made by a client
to be shown to other multiple clients.Like the chat application is one of the best example.If any of your one client gets offline then all others can se that he wents off line.
The thing is that normal http service based approach gives the server response to the only that client who made the request while
with the Blaze DS the response is send to all the clients and who ever is interested he listens that.Using Blazed DS means you
are using the Messaging i.e. producer and consumer approach.