Let's say one thing is good, but the other thing is better. In Newspeak they would be would be "good" and "doubleplusgood".
So how do you compare two things in Newspeak?
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You're almost there. "I like A better than B" would become "A is good, B is plusgood", leaving room for a third item that is "doubleplusgood".
Or again, if you want a stronger version of "good", what sense is there in having a whole string of vague useless words like "excellent" and "splendid" and all the rest of them? "Plusgood" covers the meaning, or " doubleplusgood" if you want something stronger still.
In the end the whole notion of goodness and badness will be covered by only six words — in reality, only one word
1984 - Chapter One.