Honestly both keyboards are good, but I like how Razer's BwC Has brighter backlights, as well as a less pronounced click as it's actuated. I also like not having to install two software suites, assuming I am able to get the BwC.
I have seen many good things about the Corsair keyboard, but it's just not as bright. Plus there is a lot of light leakage outside of the keys, where as Razer's products keep the light show limited to the keys themselves. You won't be getting any light pollution when you go Razer, however you get what some might say is better switch selection from the Corsair. Either way they're both decent keyboards.
Das Keyboard is what I would really like but seeing as the newest model from them isn't backlit, I see no point in choosing outside of these two options here.
I have owned a BwC and I sold it for my Ducky Shine 3. If you need true RGB then I guess you should look at BW but their switches where just... "meh" to me. The design is unprofessional to boot so it would never make it to the office. I dont know what you mean by there is no light leakage in the BwC. The keys are spaced so you can see the white backplate and the color leakage underneith the keys, the keyboard is specifically designed for that and it makes the colors seem much brighter. I suggested a new poll option as an alternative.
I mean relative to the corsair model which billows out color from underneath the keys. Every demo of the BW(C) I have seen has relatively none, to minimal light billowing out from underneath the keys themselves. Yes I know the underside is white, so as to better reflect the light from the led to the key itself. As for the BW(C) looking professional? I don't think the Razer design team ever considered making it look professional. Well not a professional work space keyboard any how. Maybe a form of "professional" gaming board though. Seeing as a lot of streamers will use it, or some youtubers will also. And seeing as they make money using it it's a profession. So maybe professional in an abstract way. :D
Either way I am just more acclimated to the way their keys are spaced. As for Ducky Shine, not my thing honestly.
Razer uses Kailh switches with raised actuation points, I tried both the Oranges and Greens, the linear switch is alright but the tactile one felt a bit rough.
Not as nice as Cherry MX and I firmly believe that the Corsair option is the superior one.