Alright to begin with I am pro MSR Carbon Reflex and just bought one two weeks ago. First things first, that $500 price tag! I agree with everyone, that is a ridiculous price to pay for any tent! In fact, if I had to pay $500 for it, Im not sure if I would have gotten it (I probably still would have because I like it so much, but it would not be an easy decision.) I would say that in order to have peace of mind, I wouldnt want to pay more than $400 for this tent. However, if you are like me, I got mine for $307. And as Dan mentioned he got his for $355. This is with tax, shipping, and everything. You just have to keep an eye out for some deals. Now that I have gotten mine for $307 I would never think twice about it or look back on the purchase with the doubt that maybe I shouldn't have bought it.
As mentioned, its fantastically light. We all know that though. The carbon poles seem extremely sturdy to me as well. I dont see them breaking unless you stepped on them or are a polluck that likes forcing things into places that do fit. However, thats another thing; the poles do not require a whole lot of tension to put them into the grommets, this is the main reason why I do not think anything will go wrong with them. As Dan as said, MSR warranties all of their stuff. Obviously wear and tear issues are not covered, but if a pole just so happens to break, it specifically states that they will be glad to replace them. So no worries in that regard.
Once again, Dan is correct with the durability and thickness of the bottom of the tent. It keeps things ultra waterproofed and may leave you feeling comfortable enough not to buy a footprint (while it will cost me in weight and I really don't think I need one, I still am going to a footprint to extend the life of my investment as best as possible.) Speaking of waterproofed, MSR has everything already seamed sealed for you. I believe Dan is correct in saying that the Scarp requires you do seam seal it yourself. Pft....If Im buying a $300 tent, I dont want to have to buy the extra supplies and go through the extra work of having to seam seal it myself. Others may not mind. Hell some may even love to do it on their own, because it reassures them that the seal it laid out in the manner that they would like it to be.
As far as the fabric not being flammable, I dont plan on cooking in the tent, so I dont really care about that. And then there is the extra headroom, I'm 5'7 so Im not one to speak on matters because it really doesnt make a difference to me.
The only complaint I have about the Carbon Reflex is that I wish the tent was maybe 4-6 inches wider. I know thats nothing, but I think if it had just that little extra space, it would be the all time perfect tent. However, it should be mentioned that two regular Prolite 4 Regular sized mattresses fit in there just fine!
The pros about the Scarp, dual doors. Whooop Deeee Doooo. Here is my opinion on matters at least from my own personal standpoint and sleeping patterns. I am not a heavy sleeping. I don't mind being eased awake when someone wants to ask me a quick question or when my girlfriend gets out of my bed at home to do something in the middle of the night or when the door squeeks open as she leaves. When all of these kinds of things happen, I take notice of them and then its lights out for me. I am not the type of person where if you wake me up, thats it Im up and cant go back to sleep. I just open my eyes quick and before you know it everything goes dark again. So enough said on that matter.
As far as the Scarp's extra room is concerned, that is the only thing that I think it beats the MSR on. As I have said the MSR would be perfect if it had a little extra room that the Scarp does. However, since this is the one and only things that catches my eyes about it, its not enough for me to ignore the many great things about the MSR. When going ultralight, sacrifics need to be made in order to go as light as possible. That being said, the only question that needs to be answered is what sacrifics are you willing to make and which ones are you not will to make? I can bare dealing with not being able to roll around at night as much as I would like to, because at the end of a long days hike, Ill probably be ready to sleep like a log. However, I know many people are not like me. In fact, I think 80% of the people on here and the ones I have come into contact with do not have "less tent space" on their "willing to sacrific" list. They of course make other sacrifics instead which is totally cool, to each their own.
Goodluck with whatever you decide. Weigh your options out and think about your "willing to sacrific list." Also let us know where you are leaning to and why. People ask questions on here all the time, but half the time we never get a follow up on their conclusions. I am interested to know which route you take and why you have taken it. Thanks.