If you want your keys to have a backlight to them, or just WASD, then go with the Lycosa. I'd go with the Tarantula based on looks myself but they're both really good products.
I would go with the Tarantula. I've heard of people complaining about ghosting problems with the Lycosa. You may never experience those issues, but I wouldn't chance it. The Tarantula works and has had some driver updates as well.
I do think the Lycosa is much better looking though and some might really want a backlight (though it's really not so good on the Lycosa).