depends on size and what you are planting, in my opinion.
if ya doing more manual labor in planting things. such as a walk behind seeder, for corn, beans, carrots, raddishes, and like. having a fluffer / looser dirt. can make your manual job easier. and a tiller would more likely be your friend.
now if ya had something that hooked onto a tractor. and you just drove across the area to put seeds into the ground. then a plow / disc. would more likely be your friend. due to less time it would take to get things done.
i have a plow, disc, and drag harrow. ((see my signature)) it does a pretty good job and much faster than a tiller. i honestly do not plant a garden. to much other stuff. but for yard work and re-landscaping and smoothing out things for replanting grass seed. i would say it did an excellent job. and was much easier to use than a tiller would ever been. actually i just tossed grass seed out. then re hit everything a couple times with the disc again. to work the grass seed into the dirt a little bit. and initially coming up, grass was a little spotty, but by years end. it had nice full growth, and no spotting. exception were i though had things right and ended up with a couple low spots were water collected some.
but again, i did not have to use any sort of planter/seeder to put the seeds into the ground. and that alone can make a large difference more so if it was all down manually and no use of a tractor.