rpaperaliterally everything. their switches are noticably inferior to corsairs Cherry MX offerings, the lapboard itself somehow manages to be heavier and less well balanced than the K63 even though it doesn't need a battery, the keyboard on the SOVA isn't removable, the mousepad on the sova is a hard plastic surface type which I personally disliked and while it's removable they don't actually offer any soft replacement so you have to kludge your own if you want a soft top, and lastly and probably most irritatingly Roccats software is so bad it's almost unusable, whereas corsairs is actually decent for gaming hardware software.
WHEW, ya its a mouthful but the SOVA just sucks when you compare it to corsairs lapboard solution, there's no competition, corsair k63 all the way.
DavePastrythe only things I really liked better about the sova was that since it was wired it had the USB extention plugs on the rear so you could tether a wired mouse to the board itself, I use a wireless g602 with my corsair lapboard and it is kind of annoying when I move it around the mouse often will slide off and bounce under my couch, but still, no contest: K63
DavePastryDepends on what you want. I bought this over the K63 because I like wired better, the keyboard doesn't come out allowing for very quick and easy movement to and from the couch, this has brown switches (from what I have read) and it has great cord management for my mouse. Plus, I actually like the design better. I will likely write a review when I get it. Especially if it sucks.
RM60SOVA has TTC browns which they claim are "comparable" but I found them to be pretty unsatisfying when compared with true cherry switches, also the K63's keyboard doesn't fall out when you when you move it around, it's secured with two latches. I hope you like the SOVA, but having owned both, the sova feels cheap and poorly thought out, especially at the price.