I do some of each. It depends on what the quilt is going to be used for but also on how the back is looking. Mostly I just take a few tiny stitches and then snip. I think that taking tiny stitches/backstitching may be a little more sturdy for a quilt that is going to be used a lot and machine washed etc. But I have also done a fair amount of knotting and burying. When I knot and bury I bring both threads to the front, tie a tiny knot and then bury. It's easier for me to do it from the front and I really can't see any difference between ones that I've done that way and ones where I've taken the threads to the back and then knotted and buried.
When I do the tiny stitches/backstitch/snip thing I always bring the bobbin thread to the surface so I can snip both threads at the same time.
What I generally DON'T do for quilts where the back will be visible is backstitch or take tiny stitches and then use the cutting function on my machines. I have two machines that will pull the threads to the back,cut the thread and tie off, but both of them leave some visible thread that is hard to get rid of and I don't like. This doesn't apply to pieces that I mount on board or stretchers so the back will never be seen--those I'll happily use the thread cutting function on my machines.
Rob