I am going to make this short. I have owned and used all three Ping drivers listed above. The G2 G5 have larger sweet spots than the Si3. But if you hit the center of the driver face on the Si3 and the G2, you...
There is no major difference. If you want the newest stuff on the market, go a head an buy, it's an excellent driver. The G2 is the real deal, just not the latest model. The G2 is older, but just as good, and...