The Grevil geo is quite relaxed, but that can be mitigated with a slammed or longer stem. The bike still looks aero, and based on the reviews I've read, it feels aero too. That said, I couldn't find any data to confirm or disprove this point.
As for the Seka, they have a solid reputation, and their frames look pretty nice. The quality seems to be there, and their QC and after-sales service are reportedly good too. But I have to admit, 3K€ is quite a lot. You can get a Grevil clone from Peter (XMCarbonspeed) for less than a quarter of the price, with the reassurance that QC and after-sales support will be good as well (per the lots of good reviews of XMC on this forum). I mean, for 3.3K€, you can even get a real Pinarello Grevil F9 frame — so why choose Seka over a Western brand if the prices are the same?