I've been going through a similar shopping experience for the last few weeks. I've decided upon the 2531 (updated version...due out within days, if not sooner!) over the 2541--stability over portability, so to speak (the 2541 is smaller when collapsed).
With respect to heads, I've also noticed that Markins seems to get more raves on this forum than RRS. On the other hand, when I check some other online resources including NAPP, some photographers' blogs, other websites, etc., I also see a lot of positive comments on the RRS products. In fact, the people at NAPP are crazy about the RRS heads (I've written to them, too).
I have also checked out the weight issue and found (from each website) that with regard to the Markins M10 and RRS BH-40 (comparing both "midsized" heads), the RRS is actually slightly lighter (479 grams to 498 grams). Not sure the load capacity is important for me---both manufacturers recommended their respective mid-sized heads to me, based on my gear, and told me they would be more than fine.
I've called both companies and they are both very proud of their product line....and I'm sure that both are "fine." I am leaning toward the RRS at this point...visceral reaction, I guess. I'm sure it becomes a matter of personal preference where either will be fine--that is, no "wrong" choice here. At this point, I am ready to go with the 2531 and the RRS head once the tripod is available. Of course, this is subject to change!! (A friend of mine got the Markins the other day and he wants me to come over to see it.....oh oh!!)
By the way, I asked Markins why so many people on this forum seem to swap the clamps off their heads and he told me that less than one percent of their users do that. I was surprised, based on what I've read and seen here!