Dual code reader ports?

[NVRider]

Hello there. I have just purchased a 98 Z3 (M44) and am getting ready for my first wrenching job of changing out the fluids. I noticed that a code reader comes in very handy for fault codes and oil resets. I have researched the threads about different readers the members prefer and am ready to purchase one. I was going to get a 20-pin reader, as I have the connection under the hood/bonnet, but also have a 16-pin OBD connection on the passenger dash console. Is this normal? Does it matter which connector for the reader I get? Will they both give the same reading? Am new to all this and am still waiting for my Bentley manual to arrive.
Thanks in advance for any help you can lend.

 

[littlefeller]

you will get more access to modules with the round plug.

 

[Antm72]

As said you get access to far more systems from the port under the bonnet than in the car on a zed

 

[NVRider]

Okay, thanks! I guess I will get the code reader with both the 16 and 20 pin connections.

 

[Brian H]

The OBD port in the cabin was introduced for you guys in the US market, something to do with emission monitoring/testing? Only a few modules of the car are connected to the OBD inboard, the rest are available from the 20 pin connector under the bonnet (hood ).