Ive owned all three saws that are being talked about in this thread and loved them all.
The 241 is a little screamer that comes in a lighter package and loves for the whole bar to buried in wood. These saws are well worth the money. Only down fall that I seen was that the power head was just as big as my 550xp. In a sense, if 2 saws are the same physical size, but one stronger than the other, why keep the smaller of the 2 regardless of the weight difference? When I needed to move some saws, as much as I liked the 241, it was the easiest to part ways with. Either way the 241 is an awesome saw and will handle bigger wood than you think it would.
My 261cm happens to be ported. I never ran it in stock form. What i can say about my 261 is that it isn't as much of a rev monster like a 550xp, but it has some very good torque matched well with enough speed for limbing. My version of the saw happens to be the "o.e." which weighs about a half pound more. Is the weight difference noticeable? Yes and no. In your hands, the 261 might feel a little more chunky than a 550xp. I feel the 261 is great for a much wider array of wood sizes, especially if you are going from limbing, to bucking to noodling. Ive tried a few different bar/chain sizes on this saw and I've always gone back to the 18" .325 setup. It balances well for me, handles well and your still getting optimal power as well. I always want the longest bar with the most power when I'm out cutting. The 261 is still in my lineup... for the time being lolololol.
The 550xp is a small, nimble package that is a rev monster yet still packs a good punch for bucking. Out of all my saws I've owned, I have the most trigger time on this saw as I use them at work too. At my job, we use them for a lot of brush clearing, limbing and some bucking. These saws handle amazing and balance well. I also like the 18" .325 on this saw too. This is a great saw and one of my all time favorites next to my ported 2153. If I didnt have my 2153, I would still own my 550xp.
Its all about what your needs are and its also dependent on the other saws that you may have. Both saws that your asking about are great saws and you can't go wrong with either one.