Hey dudes, the title says it all!
Punchbag is better but takes up more space and costs more.
dumb bells, i just started lifting and bicept curls and fore arm stuff is where its at
dumb bells all the way
dumbells for instant grattification both ftw
it depends on what you are trying to accomplish, dumbbells would would be better for strength and toning whereas a punching bag would be better for agility, punching accurately and endurance.