I have two. The strongest is the 18 volt Dewalt. The easiest to use is the Craftsman 19.2 volt. The trigger on the Dewalt is a joke plus it is real heavy so I rarely use it. The Craftsman is lighter and has a much better trigger setup.
You can see the difference in the pictures. The Craftsman has a separate direction control where the Dewalt uses a rocker switch. The rocker switch would not be so bad but it is back words. You hold the top to loosen the bolt and the bottom to tighten the bolt. Half the time I spin the nut off when I go to tighten a bolt. Plus you have two fingers on the trigger so it puts more load on the others to hold up the heavy impact.
The real difference is cost as well. You can find the Craftsman on sale with a charger and battery for $125-140. The Dewalt is going to be at least $50-75 dollars higher.
So where you are saying you are not going to be using it all of the time and even then just on mower blades the Craftsman should do everything you need. I think you will find after you own it a while you will be using it all of the time. I know I grab mine many time rather than drag an air hose out for simple things. I liked the 1/2 so much I bought a 3/8 one too. It is lighter and smaller so you can get into littler places. Great for hood bolts and such.