It looks like I'm going to be building an upper for myself soon. I'm looking to build a light weight upper for a calling gun so I'll probably go with a 16" light weight barrel. I notice I can get 16" barrels with either carbine or mid-length gas port holes pre-drilled. My question is is there an advantage to one over the other? If so what are they?

They say everything happens for a reason.
For me that reason is usually because I've made some bad decisions that I need to pay for.