I don't know why reverting to Latin roots is better than using plain English, if English is being used. I say this because I would generally prefer a return to the Latin Mass (though that is probably my only convergence with the SSPX) and so I don't want to make it sound like I dislike Latin.

The point is that "consubstantial" is just as foreign to the average modern Catholic as saying "homoousian" or something like that. "One in being" is a better and more vivid way of saying it for an English speaker.

I see that they're trying to align the Creed with the Greek original (via the Latin translation) more, but I think that choosing those sorts of words will remove the immediacy of the words from the congregation. Of course, if the congregation still knew Latin, I wouldn't feel that way.

There is a certain vagueness to English (something I've said before) that other languages lack. Greek is extremely precise and particularly well-suited to theological discussion. Latin is not as precise but still far more precise than English. The goal is to regain that precision, but the proposed solution falls short. In summary, I say either keep the Creed as it is or go back and put it all in Latin.