Well, I can say there is totally different indications of the Total etch and Self etch.
Total etch is more preferred when cavity walls are more in enamel like in shallow class 5 or shallow class 1. In such situations Total etch creates more surface area that helps in increasing bonding. Self etch is not able to create etching of hard enamel.
Self etch is more useful when more of the cavity wall consists of dentin like broader class 2. In case of Self etch you need to apply agent once only so that it is less technique sensitive compared to multiple applications of total etch like etching, priming, bonding etc. These all procedures may not be done completely without contamination on case of uncooperative patients or in case of posterior areas with heavy salivation so here Self etch is more advisable.
Though here etchant remains inside the bonding layer, there is not enough evidence of increased sensitivity with this technique.

There is on going debut what is better but then also 4 th generation bonding is still the "Gold standard" of all.