We have this conversation a lot on here. Most of the pros and cons are well thumbed. But to add a few:
Notwithstanding Phils comments about top end kit being more resilient,
any component will fail sooner if covered in crap.
It doesn't have to be raining for the roads to be wet. There are few dry roads between November and March.
Few of us have the luxary of being able to choose when we go out - there's a window of opportunity and we have to take it, whatever the conditions.
Race-blades keep the worst off of the rider, but offer little protection for your stead and next to none for your mates.
Look around on a typical clubrun.
Most experienced and serious riders are properly kitted out for the conditions - I don't mean just a cheap disposable bike, but one designed for the occassion.
Have you ever stopped to think what's in that stuff flying off your wheels? I doubt much is water! Salt, excrement, pesticide residues, deisel, oil..... I remember arriving at a cafe once when a rider found some rabbit entrails spread across his helmet.
Things have changed though. When I started, and it wasn't *that* long ago, everyone had a club bike first and when they got to their first event they took the guards off and fitted lighter tyres. Then if they got keen they'd buy a posh racer - but even then with clearance as in three year's time it would become a winter bike.... Most new riders now do it the other way around. God, I sound old.
As Dave says, its your money.
