STCC vs Determine Applicable Regimes

Hi,

We have found ourselves in the situation where AP invoices created from AGIS transactions are adding 2 tax lines rather than the desired 1. The two tax lines are being derived as follows:

Line 1 - From AR (this is the only line we wish to calculate)

Line 2 - From E-Tax (as we are using the Determine Appliable Regimes option and we have two appliable regimes for the transaction)

I discovered that when I change the Regime Determination Set from Determine Applicable Regimes to STCC that we only get line 1 - which is great, but I don't know if this will impact any other invoices created outside of AGIS. My question is - what is the difference between STCC and Determine Applicable Regimes and are there any drawbacks of choosing STCC?