anyone owned both and can attest to the difference between run time and aggressiveness of the two? obviously the fuel is going to have some advantages, but how big are we talking? i was looking at how worth it it will be to use cordless tools at work and home. the grinder has always caught my eye, but if the run time isn't too great, i don't want to dedicate a couple of batteries just to the tool itself just to get good use out of it when i can have an extension cord handy for the corded version which is a quarter the cost.