Tend to use dumbbells for this sort of this sort of thing myself. Seem to recall reading something about their conferring some arcane physiological advantage over a barbell. Is there anything in this, or is it a pile of gash?
In practical terms, dumbbells do let me work without someone to spot. However, I'm beginning to think that a barbell might be easier to achieve progress with, as it would allow me to add smaller increments more often (cast dumbbells only in my gym, going up in 2 kg increments).