Riding mower blades? That is not at all enough use to justify a cordless impact wrench, BUT, it is your money and you are entitled to spend it on whatever you want.
You should look up the torque spec on those, then you have a baseline for torque needed. Torque costs money. If you don't need 500 or more ft-lbs, you would overpay a lot to get a tool that has more torque than you need.
More significant is whether you have a cordless tool set already and can get something using the same batteries you already have, even if it comes with one then it is another battery compatible with your other tools and using the same charger is nice too. There are many brands of impact wrenches that can take off mower blade nuts torqued to the appropriate spec. You don't need the "best" one for that, nor to overpay for it.