There's really not much reason to get the modified-GG subs. We (gg) release at 1280x720 now (since the show switched at ep 11), encoded from the original digital source (a 'transport stream') - a single encode step from the source. The "modified" and "foganime" versions, on the other hand, are almost certainly twice-encoded versions of the original, i.e. one more encode step than ours. A second encode step only reduces quality irreversibly, and the only thing you gain is...fancy karaoke. Any slight improvement from the slightly higher resolution is doubtable, since Frontier was clearly not made at 1080p resolution, but it's completely negated by the terrible video filtering they apply (over-warpsharping, resulting in distortions of shapes.) Frontier was not made at 1080p, but it's been upscaled to and broadcast at that resolution - thus, most reputable encoders resize it to 720p for release. The extra 'resolution' is basically wasted bytes.
edit: Screenshot comparison: http://www.itsnotlupus.net/macf/ - check out the loss in subtle details. If you were downloading the modified/foganime versions for higher video quality, you're making a mistake.
Kei is Chihiro, actually (translator split off). They rely on reasonably accurate Chinese subs which I refer to as well, but we always wait for our video capturer to obtain the Closed Captions in Japanese for us so that we can be absolutely sure about our translation (and we spend some time in the edit/quality checking phase). Hence they have things like "Cliff Spark" instead of "Griffith Park". Video encode-wise, ours are certainly better since Kei/Chihiro doesn't have access to transport streams - they're a purely speedsub group, "translate --> timing" being their motto.
We used to provide transport streams along with Closed Captions to Lunar as well, but due to some issues, we stopped at ep 11 or thereabouts, which may explain any fall in their translation quality. I can assure you with some confidence that we have virtually no outright translation errors, with the sole exception of maybe a few small ones in ep 9 (for which we couldn't get closed captions due to a messup).