Ugh... While I respect Squeeze's experience and opinion I also really dislike thigh rigs. I find they are always banging the gun into door frames, steering wheels, center consoles, and digging into the seat in a vehicle. When out of the vehicle while hunting they drag the gun through every bit of low brush along the way. If that brush is wet your gun will get soaked, if it's dirty or dusty same for the gun. Sitting on the ground grinds the grip and end of the magazine into the ground. Not for me.
The absolute best I've found for this duty is a tanker style holster. El Paso Saddlery makes a good one. I prefer the Diamond D Guides Choice made in Alaska. Easy on, easy off, extremely adjustable, super comfortable and carries the gun immediately accessible yet out of the way. Be it thin summer clothes or heavy winter wear, no problem for the Guides Choice holster. I've worn it while scouting sign in hot September and in frigid January. It goes inside or outside a jacket easy peasy. Works fine with a backpack. I have shot deer at last light then gutless deboned, quartered and backpacked them out by headlamp all the while wearing my G20 in this holster without the slightest hindrance. I think if I should ever be unfortunate enough to be ground grappling with some large hairy critter this holster would keep the gun immediately accessible when other carry methods might not. My experience...