OBS quality is pretty much abysmal.
And it eats a lot PC's performance.
Take a look at the video I linked above and tell me again that OBS' recording quality is abysmal...
OBS looks better for a given bitrate than virtually any other recorder because OBS uses x264 which is an extremely mature software h.264 encoder. There is a performance hit, but it's quite modest if you have a strong CPU, and because the compression is so good you are almost never limited by disk write speeds.
nVidia has its own free thing.... shadowplay i think is the name
AMD has Raptr - it was mostly not working more then working last time i tried, perhaps they fixed it since i last checked.
NVIDIA's NVENC (what Shadowplay uses), AMD's VCE (what Raptr uses), and Intel's QuickSync (available to almost everyone with an LGA-1155 or 1150 CPU) are hardware solutions that have minimal CPU overhead, but they need quiet high bitrates to produce acceptable quality.
The average bitrate of the video I linked to above is about 17Mbps. To get similar quality from hardware encoders bitrate needs to be nearly triple, and many implementations aren't even capable of the settings I'm using.
DXtory works same way no performance loss (unlike OBS) but it is not free. :-(
However the file size of these raw files are giant you need big disk.
Recorders like Dxtory achive high quality with low CPU overhead by using little or no compression at all, so the raw recordings are enormous, as you say. A potentially greater hindrance is that the bitrates of minimally compressed video at high settings are huge, and few drives can keep up with them.
I record 2560x1440x32 video at 60 fps. An uncompressed video of this resolution and frame rate is 843.75MiB/s (6.75
gigabits per second); even if you drop the alpha channel you are still at 5.3Gbps. You need a RAID 0 of fast SSDs to even record this without stalling/dropping frames, and you'll fill $1000 of SSDs in about 20-30 minutes.
It's also not wise to continually write enormous amounts of data to SSDs because NAND has a limited number of writ/erase cycles. Play games for two hours a day on average while using an array of 500GB SSDs as a prerecord buffer, and you'll use up a full 5-10 P/E cycles per day. Good drives may still last a few years of this, but they won't last anywhere near as long as they would have under more normal use. I record to HDDs, which have effectively no limit to how much data can be written to them, and I can hold orders of magnitude more compressed video per dollar on HDDs than I can uncompressed video on SSDs.