I don't know about those bits, but I bought a Greenlee "Flex" bit...3/8" x 60"..auger style, and used it to go thru 3 joists.. separately of course, and the darned thing is all worn and pitted already...and they charged me about $44.00 for it...I am NOT a happy camper...if anyone does alot of old work high hat cut-outs in old plaster ceilings, the Greenlee 6" grit blade hole saw is pretty good..don't get the 'toothed" one tho'...burned that out in 2 holes...
AR
