I find the Biblical version better written
Maybe in English

My impression is that, by comparison, Islam is more rule-focussed on the grounds that the principle cannot be separated from the rules.
The reason for this assertion?
'Turn the other cheek' is perhaps the single most morally impactful of all the sayings of Jesus. The line you quote from the Qu'ran (“Not equal are the good deed and the evil deed. Repel with that which is fairer and behold, he between whom and thee thereis enmity shall be as if he were a loyal friend.” ) is not entirely equivalent in meaning. For one thing is it a little harder to understand. In fact it seems to be closer to a different Christian principle: "Two wrongs don't make a right".
What’s hard to understand? Find me a single place in The Bible that says, “Two wrongs don’t make a right.” That actually comes from Aesop (“two blacks do not make one white”—although I’d like to add that the morals were not explicitly stated in the original version of the fables and are instead the interpretations of later compilers). I’m pretty sure that “turn the other cheek” is the “two wrongs don’t make a right” part of The Bible.
Parables like The Prodigal Son also add very powerfully to the message of empathy and understanding with weakness.
The parable of the prodigal son is one of two analogies used in response to the Pharisees and scribes criticizing Jesus for consorting with lowlifes. The first is about a man going out of his way to rescue one stray sheep and abandoning ninety-nine others in order to do so. This follow-up tale about the prodigal son is much along the same lines. Note the resemblance that first story has to 2 Samuel 12:1-13, which also ends on a note of redemption. The subject is the forgiveness of sins by way of divine grace, not human beings having empathy for each other.
In contrast, the message I take from Muslims is much tougher with an emphasis on the need for you to make the standard, or else. (eg people are always telling me I'm going to hell.)
I’m surprised and puzzled to hear you speak of Islam and not Christianity as being the “people are always telling me I’m going to hell” religion. It’s Bible Bangers (mainly Protestants) who are infamous for that, at least where I live—and from what I can tell the worldwide web is very much the same. I thought that was common knowledge. Try finding me an Islamic website with a name like this.
Other powerful phrases such as 'Render unto Caesar what is Caesar's' and 'Father forgive them for they know not what they do' seem to be absent?
The latter is, false context aside, essentially just the Islamic doctrine that we are judged for our efforts or intentions and not for our successes or accidental actions, which is established at the end of surah 2 and elsewhere. The former is mentioned in various ahadith but if you want something from The Qur’an specifically then to give a quick answer you could say the knowledge is dispersed across 4:59, 5:1, 6:152 and 7:26.
If it's powerful phrases you're looking for, it's not like The Qur'an isn't extremely famous for them. As in "defining the entire Arabic language" famous.
Overall, based on this, it seems to me that Jesus in the Koran has a relatively minor role with little to say that's new or impactful? (I understand he is supposed to be simply another messenger.)
Minor role??! 43:61 speaks of him having a role in Judgment Day itself and the hadith collections fill this in with all sorts of humungously major details. Are you not familiar with them?
Finally, is there anything wrong with having little to say that’s new? The essentially Methodist writer on religion Huston Smith said the same thing about Jesus. In one of his books he talked about how it’s often been observed that practically none of his words in the Gospels didn’t consist of a quotation from the Old Testament or the Talmud: the trick was how he applied the message. And it was the Christian theologian C.S. Lewis who said that the common thread between all the great moral teachers in history was that they were invariably sent not to invent but to remind.
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