Megs 105 is vastly superior to G3. It's technically way more advanced I.e. no dust, sling, higher quality abrasives, safer cut etc.
But 105 is the 2nd most aggressive compound on the detailing market in high quality compounds. It only works on rotary or the Bigfoot to its full potential (unless your running the microfibre system in a d.a. But be careful it's very aggressive and in the wrong hands will struck through lacquer in seconds. Either way you will need to refine it unless using it on a Bigfoot and your skilled in finishing compounds down. I'm guessing your wanting to remove heavy swirls?
Cheers Mike