for any of my airsoft, I use the heaviest weight they are happy with .. (although for cost effectiveness my SAW uses madbull .25's)

when I first got my Desert eagles they only saw BBbastard .3's .. and they are down right scary with them. now my beloved Eagles are a little worn, so they get fed BBbastard .28's .. if it's cold I'll drop down to .25

now.. for most pistols in airsoft... .28's, .3's might be a little excessive... but for around 1.5 years I used my pair of eagles as my only weapons .. outdoors .. and even do now and then for kicks ... on top of that I know without a shadow of a doubt at any time for whatever reason, I can set aside my AEG and very much stay in the fight against other AEGS with just my Pistol(s)

honestly I suggest you purchase a bag of each .. .25, .28, and .3 .. and see which you would rather run