So here is my contradictory and probably unwelcome 2c:
What are you going to do with the rifle? Is the name of the game punching paper? Hunting? A little of both? How much does silence matter to you?
Because of the unusual way the airgun equivalent of load development works, there was a real charge up the calibers to get to .30. Now there is a bit of a walk back down as we see people competing with diablo pellets primarily in .22 and .25. So really, between the two, there isn't technically a "wrong" choice.
My opinion is that, for target shooting, .22 is the better option. The pellets are cheaper, you get more shots per fill, and it is every bit as accurate as the .25. Part of the game when target shooting, particularly with an air rifle when you could be using a firearm, is low cost fun and learning to read weather conditions. People are quick to say .25s are better at fighting wind, but A) is that what you actually want and B) if that is what you want, is the .25 the best choice? I'd argue .22 slugs are better at fighting wind than .25 pellets, but that if fighting wind were your game, a centerfire rifle will do you even better...... which is why people walk those targets out further to challenge themselves and the power/caliber climb continues. Thus, for me anyway, target shooting with a .22 caliber pellet is about embracing the conditions and learning about them, rather than an all out war against them. Additionally, if targets is your primary use, with .25s you get about 25% fewer shots per fill, and the pellets cost about 25% more. Neither of those are world-ending, but if you're going on a woods walk it is that many fewer stumps you can thump.
For hunting, there is a bit of a split. .25 caliber pellets are well received, proven, and available. You want to punch critters, while .22 will do the job, there is no denying that .25 caliber pellets have more kinetic energy..... BUT, slugs in .22 seem to be the new hotness and have better ballistics and appear to have better wind-fighting properties too. They are also, in my opinion, comically expensive. I can buy factory new centerfire 5.56 ammunition for about what a certain very prominent slug maker wants for their .22 caliber slugs. And quite frankly that just frosts my cake, so I'll wait until the bigger manufacturers get on board and start making slugs at more reasonable prices or make my own. *shrug*
The big advantage to the Crown, as so many have already stated, is that you can easily change calibers later. Regarding the 500 vs 600mm barrel length, take a quick gander at a ruler and look at just how wide 100mm is. It is less than the width of my fist. You're not going to gain or lose that much power or length by picking one over the other. In a lot of ways, the Crown and Impact are very comparable, however the Impact has a lot more barrel length options. Take a look at this chart:
https://utahairguns.com/fximpact Again you're looking at a 10mm barrel length difference, in this case 600 vs. 700mm. You can see the barrel length difference in .25 and .30 costs you about 5-10fps and maybe 5 shots. Not exactly going to rock your world.
I hope this helps you make your decision. At the end of the day I wouldn't sweat it too much. I ended up with a .22 caliber Crown with a 500mm barrel, and I get about 890fps with JSB 18.13s, 100 shots per fil, and with a little luck and skill I'll put ten shots at 100 yards into a sub MOA group. At 200 yards I'll have a play, even on blustery days, with the little 4" gong. On calm days at 200 I'll chase after the 2" bullseye gong. And somewhere in the middle of all that I'll dispatch a few rodents, often through NV mounted on my scope. I've not wounded one yet.
Hope that helps.
