For me the differences are big. Coverall if i see the 90m Pics and 30m Pics in the Blog. The shape of the mountains change drastically, like when you have the 30 M result you are seeing is more of the real life shape, and 90 add other science fiction shapes changing the real morphology (this actually you can see when you isit known places).
But for see better those effects we all users should see our known places in 30m. Then we can compare to Real, better.
What i would do is a experimental version paralell to the normal version, where you can run outerra in 30m or 90m. So we can test all the areas in those months and see how real looks the mountains shapes compared with 90m. And report all the bugs for make the corrections.
Maybe with the time you also change or refine the algorithms a bit for the 30m, because with double resolution are not needing overreact in slopes as with 90 m.
We can have a torrent download and as i suggested time ago, control the folder where those data are. We can open our torrent program for share the data and at same time use the data for play.
I say that for avoid your servers from saturation. I dont know if they are prepared for on the fly downloads for each part of the earth you are visiting, while the data now is 4 times higher.
IF its not a problem you can keep this posibility. Just the user will wait a bit more for download while surfing the earth.. With this posibility people can download just the parts of the earth they play or live, so they dont need so much hard drive space for enjoy the higher resolution. (my case, i would download the entire 40 Gb for sure).