Below are the important difference between storage queue and service bus queue -
Sr. No. Storage Queue Service Bus Queue
1 FIFO ordering is not guaranteed FIFO ordering of messages is guaranteed with the help of sessions 2 No session support Messaging level sessions are supported 3 At Least Once delivery model Supports At least once, At most once, Exactly once delivery models of messages 4 No automatic duplicate detection Supports automatic duplicate detection 5 No support for dead-lettering Dead letter queue is supported 6 Message size 64 KB Message size is 256KB 7 Time to leave up to 7 days max Time is live is unlimited 8 One to one message delivery Supports one to one and one to many message delivery 9 No transaction support Transaction is supported 10 Batched receive is supported but batch send is not supported Supports batched receive and batched send both. 11 Message receiving behavior is non-blocking Message receiving behavior can be blocking or non-blocking both.
Deep Dive:
Point 1 & 2 -
The storage queue does not provide guarantee about FIFO nature. The order in which messages are added to queue may not get received in the same order. On the other hand, Service Bus Queue provides FIFO ordering guarantee if "Message Sessions" are used. If messages are added with SessionID and receiver receives the messages with same SessionID then an affinity is created and the order in which messages were added, message will be received as well.
