If you had to pick a caliber which one would it be ?

[Tonykarter]

.22.  With a Jim Gaska hammer-forged barrel.  JSB heavies. 

[Be Ready]

.25 and your good

[redlined_b16a]

I have both calibers in Hatsan guns.
Both being accurate and 1 M.O.A. capable.
My .22 likes 18-21 grains in the 28-33 ft lbs range.
My favorite tune for short(0-60 yards) range is the 21 grain barracudas at 900fps.

Longer range I like the JSB 18 grains at 900fps out to 120 yards.

.25 caliber I love at all ranges.Its tuned for 25 grain jsb at 890 fps.
The .25 is about 43ft lbs and whatever the pellet hits withong a hundred yards.Its a hammer and the impact of even a pest bird makes a loud smack.Instant death on most small critters.

.22 if ammo costband local avaliblity is a big deal.
.25 if not.
I will say there is nothing my .22 cant do that the .25 can except the fact that more power makes me smile larger.
Yes there are heavy .22 ammo but if you want heavy ammo go .25 caliber.
The fight trajectory is nearly the same.
My .22 21 grains almost identical holdovers to my .25 cal 25 grains.
Long range heavy ammo pays off.

[triggertreat]

I like both calibers and their shot count is similar depending on the tune.  Both of mine came to me accurate, but the .25 more so.  I replaced the factory barrel on the .22 with an easy to order, easy to swap out MM hammer forged barrel and now it is the most accurate of the two.  Both guns will do 1 MOA at 50 yards on my good days.

If I could only choose one of them, I would have to go with the .25 because of the extra power/flexibility.  I only say this because I hunt big critters like Turkeys, Hogs and Yotes.  For pest control around the homestead, of mainly Birds and Squirrels and the occasional Raccoon at close range, I would go with the .22 cal for less than 60 yard pest control.  The pellets are cheaper with more in the tins.

So basically I'm saying both are great guns and suggest picking your power range needed between the two calibers.  You can figure on a stock .22 to have a power range around 15 to 30 FPE and the .25 to have around 25 to 40 FPE depending on pellet weight and tune.  These are rough figures.

Since I hunt, I chose the synthetic stocks.  They are one pound lighter than the wood stocks and cheaper too, but more durable plus the all black appeals to me.

Good Luck!