Same SID for QA & Prd systems - pros and cons?

We have the foll systems:

1. Enterprise Portal 7.0

2. NWDI 7.0

3. NW 7.0 (with XECO - Ecommerce)

4. TREX 7.1

5. Content Server 6.40

6. ECC 6.0

Currently the QA and Prd systems have the same SID and system/instance no, although they are on different hosts.

We would like to know what are the long term pros and cons for keeping the QA and Prd SIDs the same for all systems.

We are already making a list, so thought we might as well get more inputs from the community too.

We already have this arrangement for the past 3 months and have not faced any major issues.

A couple of cons though:

1. Cannot use solman as it cannot distinguish between the diff servers with same SID

2. ABAP transports from QA to Prd have to be manually done (cannot use STMS)

Thanks

Prasad