The Mac OS does system maintenance stuff in the background overnight [in the wee hours like around 2-6am or so] that helps to keep it running efficiently -- if you put it to Sleep it will still do those things, but if you Shut Down overnight it will have to do them when you power it back up, which may slow things down for a while at first.
BUT.. If you run music software [like GB or other DAWs] on a Mac, DAWs usually advise you NOT to use Sleep [disable all Sleep options in Apple menu > System Preferences] because it can cause problems with music/DAW software.
I disable Sleep and usually leave my Mac [an iMac] on overnight, and shut it down when I go out. However if the Mac is a laptop there are usually separate settings in System Preferences for Sleep for when it's running off the battery or when it's plugged into a wall power outlet. In that case I guess you could disable Sleep when the computer is wall-powered [and run it from wall-power when using DAW software], but you might have to have Sleep enabled when you're out and about and it's running off the battery to conserve battery power -- I'm not sure what DAW makers recommend in that regard..