I'll bite...I have a 241, HAD a 261cm(that should say something there), have a 550xp and a 562xp. I tend to overbuy things due to the theory that using a small saw too hard will shorten it's life versus using a larger saw to less than it's design capabilities will extend it's useful life.
With that said, I really like a 562xp as a one saw plan. Light enough to be a good limber and enough snot to fell/buck decent size wood with. Even bone stock they run like they have an attitude problem and are angry with the wood. Not as angry as a ported 346xp but close.
I also really like the 550xp and I feel this would probably be you're best option. I run 3/8 18" on mine and it pulls it just fine despite what other think, with a reasonably skilled hand you do not need 70cc's to pull 3/8 chain.
Onto the 261cm...I do not own it anymore...Maybe it was a factory dud, maybe it wasn't "broken in" but either way, it was a dud. And I'm a stihl guy. It was a slug from day one. With .325 it wasnt bad but it had no nuts with the 3/8th on it. A 261 does not feel light and flickable like a 241 or 550 feel.
Enter 241cm. BADA$$ little saw. Build quality is great sans the bleeping plastic clutch cover and handlebar. The air filter is great, stainless muffler, mag cases, spring av, etc etc. It is lighter and forgive me, handles better than the 550xp and 346xp. I haven't tried .325 on mine yet. I run 18" stihl bar and 3/8 PS Picco chain. You can burry it in whatever wood you want and it will hold it's rpm's really well and keep throwing chips. I'm not saying it is the fastest cutting saw, just that it is a pleasure to use.
I love the little thing but I don't think it would be my go to firewood saw unless I do not tackle anything over about 16" and weight was a concern. Mine is a used for limbing. I assume with heavy firewood duties you would be scrapping bar/chains often as they are made pretty light for these saws. Awesome saw for it's intended purpose.
Now that you are confused, I'd go with 550xp as my first choice, then the 241. The 241 has better filtration but the 550 with 3/8 semi chisel would be ideal for cleanup work with great power and little weight penalty. In most situations, The 241 will do anything the 261 will. In your situation, I think the 562 would be overkill.
-AJ