Since you have gone for steel rims and need to stop in the wet and are unlikely to upgrade to alloy rims straight away, I think you are deserved of a practical answer...
In the wet, with regular brake blocks, the alloy rim will have a better coefficient of friction than the steel rim. This much is known and these brake blocks are the wrong ones for your steel rims. You need the brake blocks designed for the job, the ones with a leather face:
Typically these are nice and cheap, they also last a very long time. In the wet they work remarkably well on steel rims, although it can take a wheel revolution for the braking power to kick in. To work around this 'turbo lag for braking' you can put the brakes on extra early to clean the rims of water and get into a habit of having your brakes ready on tricky descents, junctions etc.
You can run them just on the rear wheel first, in that way you can see how they work and use your existing rear pads on the front when the existing set run out.
Don't let their hum-drum appearance put you off - if you have steel rims they are a performance product.
If you want the in depth on 'coefficient of friction' as it applies to bike wheels and different materials, here you go: