When would you perform Sanger sequencing? when would you perform next generation sequencing?

Sanger sequencing is nowadays only done when you know what you are expecting in a locus with very low diversity. in this case you have limited resources and only need a small result, and this will be cost effective. NGS is the gold standard for human DNA sequencing in diagnostics. it is low cost, very fast (compared to Sanger) and allows for multiplexing; different samples can be mixed and sequenced.