Adobe 1998 color space or sRGB IEC61966-2.1 color space?

I'm very confused about which color space to use: Adobe 1998 color space
or sRGB IEC61966-2.1 color space.

Most of my files were made with the sRGB IEC61966-2.1 color space
embedded (North America General Purpose color setting) but I find that
the files print with less saturation than they appear on-screen.

But when I switch my Edit > Color Settings to North American Prepess 2,
which activates Adobe RGB (1998), Photoshop asks me every time I open a
file if I want to maintain the sRGB IEC61966-2.1 color space or to
assign the Adobe RGB (1998) color space.

I've read several warnings not to assign profiles to files that have
embedded profiles.

I find that color management is the most complicated aspect of
Photoshop, despite having read about color management.

Robert