RE: Plow VS Disk
North Texan is right.
A lot of what you want depends on what type of soils you have and how much moisture you get.
I agree with North Texan. Another condition would be time you can put into your plots. If you can keep the weeds out and have enough rainfall, then you may not need a chisel.
If the soil has never been broken and it is very hard and dry like it gets here in Texas in the summer, you are going to need a chisel plow. I disced about 4 acres yesterday and the disc was turning the soil over beautifully, but we 've had alot of rain and I had previously mowed the plot.
When it comes right down to it. You will probably want to buy both. Farmers get away with doing some light chiseling 2-3" deep because they work the ground regularly. We use both depending on what we have to do. If you want to buy only one go with the chisel and run it deep 5-6" the first pass and shallow 2-3" the 2nd pass. That should be able to accomplish what you are trying to do.
My .02 cents.