Totally and utterly up to you mate, whatever feels more comfortable for you. I personally have used both methods over the years, started out using the crossfader (with both channels up full), then switched to crossfader in the middle and used the channels, then switched back a couple of years ago! A lot of ‘pros’ (or resident D.J’s who think they know everything!) might sneer at people who use the crossfader, certainly i’ve found that most clubs i’ve played at the mixer had the crossfader in the middle and everyone used the channels, but watever you’re happier with is honestly fine, theres no right and wrong in my opinion, as long as you’re not pushing the mixer into the red when your mid-mix, (i.e with the crossfader in the middle and both channels up) then you’re gonna sound fine…