Curious what manufacturers people are using and if DD is still as popular as it once was.
(Not trying to start a flame war, just honestly curious as I have to buy some more soon. Specifically
2x28kg)
I have mostly DD bells of various generations, going all the way back to the first batch DD produced (2001, IIRC) that were made in the USA. I like the proportions of the DD bells, and the E-coat finish is more robust (but not thick -- a thick painted finish is usually overly slick and leaves big divots when it inevitably chips) than painted or powder coated finishes. Unfortunately, they are very expensive. I got most of mine when they were the only brand available, I was able to take advantage of instructor discounts and buy them at a workshop that was within driving distance to avoid shipping.
Kettlebells USA is the only other brand that I know of that uses the E-coat finish. I haven't tried them, but according to a post here, the "classic" line is similar in proportions to DD, while the "Elite Precision" line has a larger handle window that is supposed to provide more room for two-hand swings and is proportioned so that each size sits on the same place on the forearm in the rack. If I were to buy more cast iron bells, I would probably give the KBUSA classics a try.
I also have a couple of Rogue bells, and they are alright. The powder coat finish feels fine, but chips easily. A lot of the bells on the market now seem to be the same generic pattern and powder coat as Rogue, with different branding.
I also have some older Perform Better bells that are terrible, although the newer Perform Better bells appear to be more similar to the Rogue pattern than the ones I have.
IMO the in-between sizes (20, 28, ...) are not necessary. When I did 10 TGUs with 16 I could do at least one with the 24. Same experience with the 24 and 32. When my press 6-8RM was the 16 I could press the 24 at least once. Again same experience with 24 and 32. So you can constantly progress through S&S and ROP with the 8Kg jumps.
That's just my thoughts for men who train alone. Instructors may need more variety for their clients/groups and for women the 8Kg jumps might be too big.
Although there are a lot ways to bridge 8kg jumps between the classic sizes, I get a lot of use out of the in between sizes. For me, 28kg is a sweet sport for being able to do a reasonable volume with good form for a lot of exercises (snatches, double cleans, presses, double front squats), where 24 feels a little too light, and 32 is a bit much. I also get a lot of use out of double 20s for complexes, where 16s are a little too light and 24s are a bit much.
For S&S, the in between sizes are probably not necessary for most people. For ROP, they may not be necessary but a lot of people find them helpful. And for a lot of programs, it makes a big difference to have the right size for the job.