From page 67 of the 919AH and 1019AH operating instructions. Looks like the 1019AH has better video up conversion:
RESa (Resolution)
*VSX-1019AH model only
Specifies the output resolution of the video signal (when analog
video input signals are output at the HDMI OUT connector, select
this according to the resolution of your monitor and the images
you wish to watch).
AUTO
PURE
480p/576p
720p
1080i
1080p
ASPb (Aspect)
*VSX-1019AH model only
Specifies the aspect ratio when analog video input signals are
output at the HDMI output. Make your desired settings while
checking each setting on your display (if the image doesn’t match
your monitor type, cropping or black bands appear).
THROUGH
NORMAL
IP CONVc,d
(I/P Converter)
*VSX-919AH model only
480i/576i analog video signals are converted to progressive
signals for output.
When set to AUTO, the signals are output with the optimum
setting for the connected display by HDMI.
When set to ON, the signals are up-converted to 480p/576p for
output.
When set to OFF, the signals are not converted for output.
AUTO
ON
OFF