Here are my amateur opinions... no doubt others will have more to add.
For working the ground, you really can go either way. Disc implements, which can be either 3 pt or pull-behind, have been around for many decades, and do a good job of breaking up and leveling the soil for planting. The condition of land you are working with will dictate whether you would need to turn the ground with a plow before using the disc. A pasture with heavy overgrowth would probably need to be plowed, whereas a former corn field might be worked OK with just a couple passes with the disc.
For planting a pasture, or crop farming in general, once you have disced the soil you can go directly to seeding. If you're putting in a lawn, though, you'd usually need some additional soil preparation beyond what can be done by discing alone.
A tiller will pulverize the soil into very fine, lawn-ready seedbed with 2 passes through most kinds of soil. It does the same for gardens, etc. Be aware that the tiller will open up the top 6-8" of soil, while a turning plow will go down a foot or more.
If you have more than, maybe 5 acres involved, or you are doing any kind of serious crop farming, you would probably be better off with a plow and disc setup. If you are doing lesser areas like putting in a lawn - one time - plus gardens, deer plots, etc., the tiller is very handy.
Finally, the box blade is definitely the tool for road/driveway maintenance, although it doesn't do ditches very well.
