I rather like vinyl on the floor, it is foot-friendly and easy to swab down. Unlike tiles there is no grout to get dirty. If it is upstairs people will not be trampling grit into it. You will probably not slip over even if it is wet.
You can have a bead of silicone run round the edges to slow down water getting down the crack.
It is relatively easy and inexpensive to replace.
Unless the subfloor is very smooth and flat, it is best laid over WBP ply (it does not need to be thick, even 3mm will do)
I prefer the floor laid first, then the WC put down. No cracks and gaps. A plumber can lift and replace a WC or basin very quickly.
Please don't tile ALL the walls/ceiling. The amount of condensation created after hot showers means you will need a monster extractor fan - my former boss had this problem. There is nowhere for the humidity to go (plaster walls absorb more than you imagine then dry out) the bathroom was permanently wet - and tiles slippery. I had to fix the problem w a new expensive extractor fan that was powerful AND quiet as it had to overrun for over 20 mins after the light went out (humidistat). I also had to shave off the bottom of the door so the extractor could 'pull' air into the room.