The schools of thought are one as stated above, the yeast are done so it shouldn't matter. The other is that if you cold crash you could shock the yeast causing them to excrete protease enzymes which would be damaging to head retention. As with everything in homebrewing it seems both schools will get great results. I have never cold crashed, I always slowly ramp to lagering temps and have had two great beers, a schwarzbier and a munich helles. So I would say cold crash it and see how it turns out, either way it's going to be drinkable. Cheers!