Diamonds can be a challenge to keep healthy because they have reasonably advanced heating requirements. However if kept well they can be a joy to own.
Jungles are known to have a bad temperament and can be tricky feeders. However I have seen a pair of snappy, difficult feeder jungles become good feeders and good handlers with persistence.
The 1.5-2m range can be a bit tricky as many morelias are capable of exceeding this. Overall I would probably say a Coastal or Inland Carpet. Depending on what state you are in and the licensing system (and your price range) you may also want to consider a Woma.