Bob,
Back in the day when I used a .22-250 what I personally found was that I could use a slightly heavier bullet than with a .223 for more energy and penetration. My range wasn't any different because I continued to hunt the heavy timber, however, I was hitting them harder with a heavier bullet in the larger cased .22-250. As an example, I tended to favor a 52-53 grain Sierra or Speer hollowpoint in the .223. For the .22-250 I preferred at least a 55 grain bullet and 60 grainers were better yet. I could tell the difference between the two cartridges, especially with a "scratch" hit around the edges of the vitals. I know, perfect shot placement is the key. However, a quick moving coyote in the thick stuff doesn't always allow the plan to be perfectly executed. So a heavier bullet in the .22-250 anchored more coyotes near the hit and within sight than the lighter bullets from the .223 on marginal shots. That's one of the reasons that I don't like the super lightweight bullets in the .243. What's the advantage over a .22-250 if you're going to shoot 55 grain bullets from each? In fact, isn't there a disadvantage in that the BC/SD is greater for the .22 caliber 55 grain bullet versus the 55 grain .243? I don't think the .243 has an advantage unless you're pushing 70+ grains of bullet. That's my take on it.