As always, the answer is "it depends".
Silicone v polyurethane ?
I believe the lightest fabrics will be silicon impregnated (unless you want to use cuben, to which this question does not apply)
Bacteria will feed on PU coating if it is packed away wet for extended times, not so with silicon.
Silicon impregnated fabric absorbs little water. PU coating is typically (always?) on just one side of the fabric leaving the fabric free to absorb water which you'll be carrying if you have to pack up wet.
Silnylon is slippery, good for not clinging to debris, but hard to not slide around on (Jim Woods has a solution to that)
In a hard rain, silnylon mists thru (or maybe underside condensation is dislodged, I'm not sure). Ray Jardine claims to have silnylon treated to stop that but I'm giving that a big fat WDKT (We Don't Know That) until I see independent test results. It only took me a couple rainy nights to stop worrying about the mist, YMMV.
Which weight ?
Ian, Ian, Ian ... I know you've been around this forum enough to know the answer you'll get here.
can one material be used for all of the tent ?
That one really does depend on the design and its intended use. Tell us more.