Hi! I may be biased since I just got a Corsair K70 LUX RGB, but here's my input.
TL;DR (Too long, didn't read): I would say to get the Corsair- the font can be overlooked, and the wrist rest/ media keys just make the experience better. Also, the software is great.
Both Razer and Corsair make great keyboards, and they both have lots of experience with making mice, mousepads, etc. Razer tends to use their custom mechanical switches, while Corsair mainly uses common Cherry MX switches. If you are happy with your current Blackwidow's features and don't see the need for extras (such as multimedia keys) then, by all means, get the Razer. On the other hand, the brushed aluminum finish on Corsair keyboards actually appears very nice and durable in person, much more of a matte finish than a (typical) matte plastic. In person, if you haven't tried the Corsair K95, the Gamer-y font actually isn't too bad, it just takes a little bit of getting used to.
About those dedicated media keys- on the K70, at least, they are AWESOME. They work natively with YouTube, iTunes, the Spotify app, VLC, and the list goes on and on. The most useful thing, I find, is the volume wheel. It's made out of knurled aluminum, and it just feels so good to scroll. (The mute button is also a plus.) If you were making your decision solely based on these media keys, I'd say to go for the Corsair.
Now, the Corsair software... The first generation, solely called CUE, was an absolute mess. It was hard to use for lighting alone, the "profiles" couldn't be easily switched between, and other peoples' lighting setups would never work quite right on your own keyboard. A few months ago, Corsair released CUE 2- it was easily 100x better. It had (has?) a simple interface, is intuitive to use, and setting up macros (I've heard, the K70 doesn't have any Macro keys) is incredibly easy. In my experience, the Corsair software is great, it just takes a little while to learn and set up fully.
Also, the wrist rest is really nice. It isn't that terrible "sticky" rubber that some wrist rests and gel mousepads are made out of- it has a nice texture, and does help to make typing really comfortable.
The bottom line- the Razer keyboard is nice but doesn't have all of the features that the Corsair has to offer. So, I'd say to go for the Corsair.
Hope this helps,
RandomGuy42