take the second shot above.
the white cloth in the exact middle of the frame would cause underexposure, and underpowered flash, if you were spot metering in the center of the photo. This would fool both the on-camera OR external on-camera flash. Using Evaluative metering would help dramatically.
I'm not saying you won't often have better results with the off camera flash, but in the examples you posted, I don't think it would make a huge difference. Most folks are wanting to bounce an external flash, and that option generally isn't available when outside.
PSA: The above post may contain sarcasm, reply at your own risk | Not in gear database: Auto Sears 50mm 2.0 / 3x CL-360, Nikon SB-28, SunPak auto 322 D, Minolta 20