I used to race 1.75 Z Max's BITD and loved them. But, 10 years on I'm clearly a bit bigger and heavier, so don't know whether I'm right to be using 1.8's now.
Widths vary between manufacturers, Conti are always narrow compared to other brands. If you are a heavy rider (not necessarily rider weight but riding style) a wider tyre will give you a larger air volume to aid suspension and help to avoid pinch flats. Narrow tyres cut through mud better to grip the firmer surface below but you need to ride light to avoid flats (ask Tintin40 about his Peaks experience on 1.5's). Another thought to consider is wider tyres leave less room for mud clearance. Always a compromise when tyres are concerned.
I'm using Maxxis High Rollers-UST Tubeless, and I love them! No more pinch-flats, just ride them until they wear out! The tread design seems to work well on hard pack, as well as shedding mud buildup, due to the wide spacing of the tread block.
I seem to be running IRC Mudmads al year round... Narrowish 1.95. nice "porc" type knobbles that clear dead well and dig in nice on all sorts of terrain. Bit weighty though... Got some Bontrager ust ACX 's coming this week so I shall be trying them next wk end...