3 bursts with 8.6mm SMG at Dex 16 bonus is hardly relevant since that is pretty much end of the game.
Regarding Full Auto, it is definitively worth it, at least for the "All rounder" build, since it gives flexibility to mix with other styles, with assault rifles or snipers. And 40% more bullets in the burst makes two burst attack be almost as effective as 3 bursts attack.
On the other hand, if STR is scarified to get advantages of DEX10 build, extra power of 8.6mm SMGs is gained with the cost of losing 30% (1-5/7) of burst power.