It all depends on the situation, as always...
First of all, you can consider why you write the criticism:
1.) Do I want the creator to improve the map?
2.) Do I want the creator to know of the issues so he can be more alert about them in the future?
3.) Do I want others to know of the pros and cons of a map so they can decide whether they wanna try it or not?
These are some approaches that I can think of from the top of my head and everyone of them has, in theory, distinctive characteristics and target groups. However, I bet everyone has a preferred style of thinking that is formed by how they learned or how they came to handle criticism and that's how the writing in any occasion is influenced by.
Revelation is in this case more of the 2.) type since he knows that time is too short, but seems to prefers type 1.) since he sees a lot of potential.
JackGriffin seems to be more leaning towards 3.). This type of criticism involves probably a different tone, maybe less instructive and more like a list of features (presented in a subjective, semi-neutral form).
Potentially, most of any upcoming issues can be solved or at least attempted to tone down. Regarding performance issues, there may be several workarounds (and probably more than the ones being listed):
1.) Delete brushes that are purely there for eyecandy.
2.) Replace basic textures with textures which fulfill several functions and in that process delete brushes. For example, if you have a trim at the bottom and a wall as seperate surfaces, choose a texture that has both by default, or create one.
I did something similar while retexturing a friend's map, not because of framerate issues, but to save Nodes (I was in danger of exceeding the limit).
3.) Think of a solution if you could block certain points of view of very high Poly Counts by adding another floor or a decoration that fits the theme. A simple example is making glass non-translucent again.
4.) Look out for actors that might cause a problem: Maybe it's just too many high shadow detailed surfaces or maybe you chose an actor with too high of a radius in general. For example, in the release version of my CTF-Dargrok I had a KillAll Actor that spanned the whole map. Everyone complained about the low framerate, and I too was surprised, as in all the testing phases, it has never been that low. Then, for the patch I split the KillAll actors in smaller ones and the problem was gone (for the most part).
I think both sides have their valid points, though, personally, I love absorbing any kind of criticism I could possibly get, even if it doesn't necessarily mean I would change anything now or later. But imo it is good to know what others think, regardless of their points, and then decide if I can make use of them or not.
BTW: I've been very excitedly following the contest since its genesis. I'll be one of the judges, that's why I've kept silent for now, but I will give my opinions on every map later by all means.