With all round CRTs, you have a choice. If you expand the vertical and horizontal to fill the round CRT and maintain the correct aspects, you lose the corners of the picture. If you reduce them to show the entire picture, you are not using the entire CRT (there will be black bars at top and sides).
Many round-CRT sets, like my Hallicrafters 505 and National TV-7W, put a rectangular mask in front the CRT, so the displayed portion is rectangular, even though the CRT is round.
If your set shows the entire CRT without a rectangular mask, then I guess it's a matter of your preference. You can usually adjust the width and height to make it work either way.
Regards,
Phil Nelson
Phil's Old Radios
http://antiqueradio.org/index.html