I read lots, many people suggested does not use AQMP-RPC for synchronous call. My response data size is 4MB, so, REST-HTTP taking too much time to send data from server to client. So, we decided to move RPC.
Can someone please suggest, should I move from REST-HTTP to AQMP-RPC or any other RPC methods like Apache Avro, Thrift or Google Protocol Buffer for sending bigger data.
You could do worse than take a look at Cap'n Proto. It's an interesting take on serialisastion, in that it endeavours to remove the need for it at all whilst still making things sane in application code. It's written by one of the guys who did Google Protocol Buffers v2. They're doing a sneaky thing with RPC too, allowing some time saving if the result of one RPC call is merely the input to a subsequent RPC call.
GPB aren't too bad either, ASN.1, etc. Anything (apart from Cap'n Proto) that has a binary wire format is probably going to be about the same - they have to marshal bits and bytes to and from a local representations. Avro of course includes its own schema with messages - pity if that's bigger than the message that's being sent.
Anything binary is probably way better than anything text (JSON, XML, etc).