18V Hitachi here too, very good, not enough power to get very very stubborn nuts though.
As for air powered, i would recommend Chicago Pneumatic, as long as the air supply is enough, dry too.
I also wouldn't buy from the people in the link, i paid for something a couple of years ago that had free post, then they tried to slug me $250 freight. asked for a refund and that took about a month, finally getting it after threatening to go to consumer affairs.