What are the differences between these sentences?

Question

How is まるで、たった今確定した事実をいうかのように semantically different from まるで、たった今確定した事実をいってるかのように?

Full context:

日も落ちかけた頃、ヒメノはふいに立ち上がり、スカートの汚れを手で払って、まっすぐ正面を見据えたままいった。 「私たちは将来、とっても偉くなるんだよ」 　彼女だけが持つ、あの透き通った声で。 　まるで、たった今確定した事実をいうかのように。 「......将来って、どれくらい先の話？」と俺は訊きかえした。

Answer 1

言ってる is an informal and colloquial version of 言っている, and it sounds fairly out-of-place if used in a solemn narrative part of a novel. So let's compare the following two phrases instead:

1. たった今確定した事実を言うかのように
2. たった今確定した事実を言っているかのように

言っている can only refer to something that has already been said, so when this phrase refers to something yet to be said (i.e., "as if she is going to say"), 言うかのように is the only option. In your case, however, the two phrases are interchangeable because they refer to something that was just said. Maybe 言うかのように might sound slightly more literary (don't ask me why), but the difference is minimal.

Answer 2

いうかのように and いって（い）るかのように are practically interchangeable in this context.

I feel a slightest nuance in focus, though. The version with the dictionary form sounds like it is referring to the speaker’s state of mind that led to her saying what she said (”as if to say …”), whereas the version with the continuous form describes how she was saying it when she was actually saying it (”as if she was saying …”).

The difference is very subtle.