The secret to success with ANY disc is lbs per blade....Obviously, the heavier, the better they'll work. Old school thinking used to be having disc blades about 6" apart. Later on, they moved 'em out to 7" +. Some larger disc's will have 9" or even 11" spacings. Typically, the wider the spacing, the larger diameter the blades SHOULD be. Larger diameter blades will also typically have more "dish" to them.
Just about all "modern day" 3-point disc's are set with 7-1/2" disc spacings, although I've seen a few with 6-1/2". A very few will have 9" spacings. Those are generally (but not always) higher end heavy duty models. Most old "drag disc's" had narrow spaced blades. They tended to try to roll on top of the ground rather than IN the ground, creating the false sensation of being "easy to pull"....In fact they ARE easier to pull, but at the expense of not working very deep. Simple "fizzix" tells us that the less work you're doing the easier it is/the MORE work you're doing the more effort it requires....
Frame weight is somewhat relative to frame strength (but not as a hard and fast rule...) As with ANY ground engaging tool, there is a great deal of stress and frame loading when working. In many cases, BOLTED frames will allow some flexing without cracking welds. WELDED frames are so rigid, there's just not any "give" in most cases. With that. welded frames CAN crack.
Also worth attention is the upper 3-point structure. With mounted tillage tools, they tend to want to rotate up and over the lower link pins.....That puts top link and upper 3-point structure of the disc in compression. I've seen a few instances where the strut running from the top link attach point down to the rear of the disc will bend or buckle, allowing the rear of the disc to raise up (and over) When applying extra
ballast on a disc, it's good to equally distribute the weight front to rear for this reason. Putting all the weight on the front of the disc frame will compound the problem in many cases.
Without a doubt, the best 3-point disc I've ever been around is an old design....The Massey Ferguson #25. It has enough built in weight, and is well balanced, so it does a great job without piling on additional weights.
3-point disc's, if set correctly and weighted sufficiently will do an excellent job. Their rigid frame levels better than a flexible frame (such as was common on older drag type and some early wheel disc's with floating gangs) After all, it's about doing the best job, not creating the easiest way to spend time....
Just make certain the frame is strong enough to handle additional ballast (if needed) and you have enough lift capacity to handle a ballasted disc.
Notched blades have an advantage when tearing up hard soils/turf. They have a DISadvantage with regards to strength and wear. If you have a lot of rocks, notched blades are more prone to breaking than solid blades. Also, with less metal to begin with, notched blades will wear down quicker. It's a common practice to put notched blades on the front gangs and solids on the rear as sort of a compromise. (As I have done on all 3 of my disc's......MF25 3-point, IH350 wheel , IH496 wheel)
Roller bearing/ball bearing disc's are great IF YOU HAVE SEALED BEARINGS....Open roller bearings need constant attention. Cast iron "boxings" can continue to function way beyond the point when wear is beginning to show. I've seen boxings with 1/2" of wear still operating with no issues. Just pump 'em full of grease before each days use and life goes on.