I’m ending my first project done from scratch with this version. My favorite change in PHP done on that release turned out to be constructor property promotion.
However, I just noticed, that there was MUCH IMPORTANTCHANGE in PREVIOUS VERSION (PHP7.4) that no one (* that I know of) is talking about — and we should: The War has come to the end!
Of course, in modern applications such differences doesn’t have any real value in terms of performance — we should consider also e.g. readability, but answering that question: concatenation with single quotes string was a bit faster in PHP7.3: You can see that with 100 000 000 concats we have 2sec difference on my computer in favor to concatenation.