depends on the situation. If I needed to lay down suppressing fire, then absolutely full auto! More precise shots would be 33 round burst. I think that it would be semi automatic fire mode that I wouldn't use
I think burst is only really useful for people incapable of controlling themselves to look after their ammo
I rarely use full auto. I've always kept to semi except when I flank a lot of people and need to quickly 'sweep' them with fire
I have 1 to 7 round burst on my SMP and I use 3 round all the time I love it for that weapon as full auto is a monster