Here's my standard answer to this question:
I'm a big fan of comp bells. I don't think there is anything about hardstyle that makes it more suited to cast iron bells or less suited to competition bells.
I have a ton (almost literally) of cast iron DD (some going back the first ever DD production run) and Rogue bells, but I much prefer my competition bells for almost anything. Other than for goblet squats and bottoms up presses, I NEVER choose a cast iron bell over a competition bell (I have a lot of duplicate sizes in both). I'm 5'9" with relatively short legs, and have no problem with clearance for doubles with comp bells. Petite women use double comp bells for long cycle with no problem.
I have both Kettlebells USA and Kettlebell Kings comp bells. My favorites are the Kettlebells USA Paradigm Pro Elite comp bells. The 35mm handle is "right-sized," the finish on the handle is smooth, but with a little grain to it that works with and without chalk, and the geometry feels really good. The Kettlebell Kings comp bells have a little smoother finish to the handles that I find less secure, and the paint chips much more easily, although any paint or powder coat finish will chip with doubles. 35mm is only very slightly smaller than most cast iron bells. You can definitely feel a difference, but it's not dramatic. There are also comp bells with 33mm handles, and that's obviously a larger difference, and the difference in circumference is greater than the difference in diameter. I've never personally tried 33mm handles.
Although I don't really do any two-hand swings, both comp bells actually have more
space under the handle than cast iron bells for two hands, plus the horns are vertical so they don't squeeze my fingers as uncomfortably as the inward curving horns of cast iron bells. There are some brands of comp bells that have narrower windows, but not these two brands.
KBUSA has an FAQ page about competition bells compared to cast iron bells for two hand swings.
Just get a bell or two. Doesn't matter which. Just get started and get moving. Tendons, ligaments, bones and muscles won't mind where the load comes from. Then, after 5000 TGU, or 100.000 kb ballistics you will have your preferences..
Yes, ultimately it doesn't really matter in terms of results, personal preference will vary, and the only way to really develop a preference is to have experience with both. But having done a lot of reps over a lot of years with a variety of bells, it's worth it to me to get and use the ones I prefer.