the grease zerk there are pros and cons each way,
most modern bearings that are used in AG use a very good seal system and really do not need to be greased (I would be more interested in the protection of the seal), I have Old JD Van Brunt drills, and they went to a sealed bearing many years ago on the disks, they last usually the life of the disk,
the old Iron on iron bearings, need greased about ever 4 hrs of use to keep from being ground to power,
now there are regreasable sealed bearings, now one needs to be careful not to over grease them, as you will blow out the seal and then it will wear out fast, but on my OLD BW JD disk they have a regeasable bearing block and they take about 2 shots of grease a year, and if watched close one can push the old grease out and clean the seals, I have lost two bearings on the disk over the years, and it is mid 1960's disk both have been seal failures, (these have replaceable seals) and I have replaced them twice now, once in the 1980's and again here two years ago.
on the grease or no grease bearings a lot depends o the try of bearing it is,
because I have some OLD stuff, (iron on iron bearings) and if one keeps them greased correctly they last a very long time, (the drills one is a 1946 and the others are pre 1960's), and most all the drive is iron on iron, (most have been used to plant a few 100 acers ever year), and they are still good, (these are not in the dirt but on the drill),
but my guess is it really will not make much difference in your situation,
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on the disks size, (the larger should throw more dirt and last longer)(but the dish of the disk and the angles set on the shank and if the shank is striaght or bent at the disk mounting location, will all make diffrences, ( look at disk plow,
http://www.ntractorclub.com/eds_stu...Plow/Master Parts Book/dearborn disc plow.jpg or
http://image.made-in-china.com/2f0j...lough-Reversible-Disc-Plow-1LY-SX-Series-.jpg see how the shank is bent so it tilts the disk so it cuts and lifts more, these I think are to big for you,
http://ronstractor.com/images/gallery/11-1/AME BakerPlow Disk Size.JPG
I would think the angle (you would set them at) would be the most important as to what or how much dirt will be thrown,
the disk size, may be more for preference of the machine, the larger will thrown more dirt and can run at less angle, and higher speed,
Also the depth at which you want to work the disk, the hub should not be running in the earth, it should be above the earth, in most instances,
a lot may just depend on what your wanting to do, about the only place I have used that try of disk is on my tree mulcher, to cover the plastic mulch edges so the wind would not get under the edge,
I do not know if there dish of the disk is the same for the size or not,
(not exactly sure what your trying to accomplish, but my guess is you would be able to adjust things to work nearly regardless of the size of the disk), and unless your doing acers and acers, a little inefencey most likely will not be a major draw back, but if you were going to go and work hundreds of acers, one may want to get all the sizes of disks avaible and dished types and do some testing to what would be the most efficient for the job,
soil types and conditions can make a lot of differences as well,
If your buying local, I would probably ask which one is the most popular for the area, and go from there,
I have used sweeps (in summer fallow) on a chisel plow for (what seems like for ever) and have tried all kinds and types of sweeps, and some that claim they pull easer, and some that claim they will cut the weeds better, and in practice, they for the most part all work nearly the same, with very little visual difference,
so my guess is the disks will do much the same,
on the dish of the disk, a lot may depend on the speed you wanting to travel,
the disks on drill are a good example,
the old horse drawn equipment normally had deep dishes as they were only moving at 1 or 2 mph, and 1950 stuff had a medium dish, and traveled at 3 to 4 mph, modern equipment have nearly flat disks on the openers or even flat, as they can travel up 5 to 8 or more mph, if one wants, and if you used the deep dish and drive modern farming speeds, you would throw soil to or three rows over, instead of just opening up the furrow, and if you use the modern disk at 1 mph you will not hardly have a noticeable furrow,
I hope my rambling helps you in some way,
