Do you want a constant 6 1/2# DAO pull (Sig P250) or a 9-10# DA pull followed by a 4-5# SA pull for follow up shots, along with a decock lever (Beretta Storm)?
I've both, though my PX4 is a full size "D" model with a 9# DAO pull. They are both great handguns and when comparing the compact models, IIRC, the Beretta will be just a tad bit smaller by a few fractions of an inch. The Storm Compact also has a shorter 3.2" barrel vs the P250 Compact's 3.9" barrel, so you would have to be more selective in picking your defensive ammo, as a short barrel length like that can play havoc on HP rounds being able to properly expand (Federal HST, Speer Gold Dot Short Barrel/+P, CorBon DPX, and Hornady Critical Defense are consistent top performers from short barrels under 3.5").
They are both soft shooters, with the Beretta having possibly a slightly faster on target recovery time because of the rotating barrel design, which does seem to help absorb a little bit more recoil and keeping the barrel in a straight line. However, with that said, you need to make sure that if you get the Beretta you keep the locking lug channel and nub lubed/greased to ensure smooth rotation.
Concerning accessories, it's not a problem finding whatever taste of holster you desire for either online, though possibly a little easier as the P250 shares many of the same accessories as it's striker fired brother, the P320.
If possible, see if you can find a place to rent both of them to shoot and see which one fits you better. Good luck!