Anthony, OK based on your last post....
I have a Daystate Regal XL in .22. I use it for backyard pest control, primarily for squirrels. Has plenty of punch and agree with all, that shot placement is critical. Therefore, accuracy of the gun is extremely important as well. I hunt 35 yards or less, with many shots being taken at 20 yards. I like the JSB 15.89 and 18.1 grain pellets. 15.98 are a bit more accurate for me, but not by much. This gun is extremely accurate for me up to 35 or 40 yards, IF...I do my job right. I also know it is capable of shooting accurate at longer distances, but for hunting in my backyard, that does not apply.
If I think I am going to take a raccoon or possum at night, I use the 18.1 grain pellets. I will say that I agree with others, that .25 caliber will have better penetration and "smack down" capability so I don't risk accidentally wounding an animal and having him run off. I do not own a .25 yet, but I am definitely getting one in the fall or early next year. Looking at the new FX Dreamline in .25, DS Wolverine R, FX Crown and possibly RAW 1000X. May even go to RS in .25. I want a regulated .25 caliber mid to high end PCP for my next air gun so I can shoot at longer distances for both target and pest control. Main reason - I want to try insure ( or at least minimize) having to shoot any follow-up shots for pest control. And, I want a .25 and another air gun.. Ha ha.
So, the reason you are getting varied opinions is because they are trying to find out what you will be hunting, how far in terms of distance and it would be nice to know if you are/will be using a PCP vs. Break barrel or not. I don't think there is a right or wrong answer here, and depending on your application either a .22 or .25 would suffice. One other mention is that some of the brands have quite a bit of power in .22 in terms of going up to 40-50 FPE, which is plenty enough for everything I mentioned here. In that case, you could make an argument for staying with a .22 caliber possibly. See what I mean - it all depends is not a bad answer for your question.
My opinion is that if this is your first air gun, go for a .22. If this is not your first gun and you have a few .22 calibers, then get a .25 if you have some of the same wants/needs as I do for pest control and small game hunting.