I personally struggle with knowing how to handle this. I'm both a reviewer seeking to provide entertaining reviews and a content creator putting my creations out there for inevitable evaluation. So objectivity will not be my strong point here. That said, some quick(not really) thoughts:
No matter what we're talking about, our speech is to be favorable even when favor isn't deserved (Col. 4:6), but nailing down exactly what that looks like in a given situation is tough for me.
As an entertainment reviewer, I probably lean toward being more sensitive with my wording the fewer people involved in the work I'm criticizing. (Though I'm sure I'm guilty of exceptions.) With lots of people involved, they can hear the criticism and shift the blame if they need to in order to feel better. For this reason I usually cut loose on big Hollywood movies, though I'm trying more and more to use subjective language even then. (Example to follow below.)
If it's one person behind it all, and they are a creative type, I'd lean toward sticking to the facts with language that is as dry as possible when discussing perceived flaws, using subjective rather than objective language.
Here's what I mean.
Subjective, dry, "just the facts" language: "I didn't notice much character development, which was frustrating to me".
Objective, colorful language: "the novel was woefully and sorely lacking character development".
As an additional note, I don't notice that Christians are especially sensitive, though some may wrongly and subconsciously appeal to "Christian love" as a reason their work should not be criticized negatively by another Christian. Rather, I think creative types (regardless of their beliefs) are those who will likely be most sensitive toward the criticism of their efforts.
I find that those who are very creative also feel very deeply, which is part of what makes their work engaging. But since they also invest personal emotion and their sense of identity in their work, it's very difficult for them to take criticism without feeling as though their worth has been reduced. Even if they know with their mind that their worth is based in Yahweh's love for them and not their creative work, the heart has trouble remembering that.
The dry, gracious language will still be tough for the creative type to hear, but will be less painful and therefore more likely to give them some things to think about that may help them. Colorful objective language will lead the creative type to mentally recoil in defense and think of the critic as a prideful "know-it-all" that can go $#@%^ themselves. In this case the criticism may never even be given any weight by the creative type.
Of course, I have absolutely no personal experience with this whatsoever... ;-)
Both sides of this equation, the critic and the creative type, have responsibilities. Neither should count on the other to take the high ground, but both should aim for it themselves regardless.
I'd welcome other thoughts on this as its something I think about and wrestle with on a recurring basis.