Does the m12 3/8 impact have enough torque? seems low compared to the m18 impact driver. but i guess it depends on what you use it for. I used a friends dewalt 20v brushed impact driver today. I think that model has like 117 ft lbs of torque. used it to take caliper bolts out. work pretty good. I am sure the fuel version would be better. if i get the 1/2 drive fuel impact yes the 4.0 batteries would be best but for basic drilling in my application i think its a waste and just makes the tool heavier and bulkier. the 1.5-2.0 would be fine as thats what i have now. the impact driver the 3.0 i think would be good. I do not see how a m12 fuel drill would be better then a m18 brushed drill. the specs do not add up at all. sure the brushless motor will last longer but i doubt the battery would on a single charge. maybe i am wrong.