It depends on what you shoot, and your workflow. For most of us, there will be very little, if any benefits, and “upgrading” to the new cards will not be worth the extra cost. To understand why, you need to understand more than you care to about how the Nikon D4s and memory cards work together. So, I’m going to give you the bottom line first, and explain why later.
* These cards may help you if you shoot incredibly long continuous sequences at high frame rates for sports, photojournalism, or events. It’s especially true when using RAW, RAW+JPEG, or possibly even TIFF (remember TIFF?) If you’re shooting JPEG only for your high-speed shots, you should see no difference. The most useful metric to apply is how many shots can you take before the buffer fills, and shooting is stalled until the camera can offload some images to the memory card. With 12-bit lossless compressed NEF files, the new cards improve buffer capacity from around 133 shots to 200 shots (under “standard” conditions: ISO 100, etc.) At other settings, the difference is minimal: 36 versus 36 shots using 12-bit uncompressed NEF, and 200 vs 200 using JPEG Fine (Size Priority.) If you’re shooting video, the increased write speed may also be a benefit, particularly if you are simultaneously outputting to an external recorder through the HDMI port while recording H.264 video to the internal XQD memory card.
* If you typically shoot large numbers of images and need to transfer them quickly to a computer (again for photojournalism applications, or just because you are impatient), the new cards can save time by cutting transfer times by half (or better) if you use the new USB 3.0 card reader or an equivalent. I recently shot 7,300 pictures at an air show and could have used such speeds.
I must admit that when Lexar’s 1100X XQD cards were on sale a few months back, I snatched some up. I liked their 168 MB/s read speed and 155 MB/s write speed. The new Sony cards guarantee 400 MB/s reads and typically offer up to 350 MB/s when writing to the card from the Nikon D4s. So, what’s not to love with the Sony G series?
In practice, the memory card is already accepting images from the D4s as quickly as the camera can supply them, with either card. So, it makes little difference whether you’re using a card that can write at 155 MB per second or 350 MB per second. You can shoot all day and the buffer will rarely, if ever, stall. You’d need to be shooting high speed sequences or video, as I described earlier, to gain any benefit.
Now read speed is a different matter. A USB 3.0 card reader can typically suck off images as quickly as the card can supply them, so transfers at 400 MB per second will be noticeably faster for everyone, regardless of whether you’ve shot 100 images or 10,000. Is saving 30 seconds or five minutes important to you? Only you can judge, but only those who deal with thousands of shots daily will be moved to upgrade to the new Sony G series cards for that reason alone.
If you’re in the market for a new card, consider the new Sony XQD card to keep abreast of current technology. The rest of us can probably wait awhile.