Reliability. Poulan ain't near what they once were. The smaller Husky's are actually Poulan clones (2xx saws IIRC) but dealer support is much better with orange vs yellow plastic IME. Saws like the 435/445/450/455/460 you can expect Husqvarna's usual excellent quality/performance.
Stihl offers near unbeatable parts support for even their smallest homeowner saws and the reliability record is pretty spotless too. That's because they are sold/serviced in a way that assures you cannot receive a saw with a problem right out of the box. Dealers are
supposed to start and tune every new saw sold before handing it over. That doesn't mean problems never pop up but it sure does make it rare.
One problem (for you anyways) with Stihl however is that new OEM parts are not supposed to be sold online (making online parts sources scarce) so if you don't have a dealer local to you, it might be a pain driving in to get what you need. Your dealer may however be willing to ship parts to you via phone transaction.
Pro-grade saws from either brand start at roughly $500 and go from there. If you're willing to go there, the Husky 346XP and Stihl MS261 kick-off the pro saw lines. Many members here own professional grade saws and will tell you they will never go back. These are the kind of machine a non-commercial firewood cutter will be hard pressed to wear out.
IMO: The Stihl MS250 is a fantastic saw for the money (comparing new saws only, StihlHead will tell you to go get a used 026 instead
) Will flat-out out-perform any of the Poulan Pro machines and is the most HP you can buy for $300. Not considered "professional grade" but there are a lot of 20 year old 025's (the ancestor to the MS250, almost an exact twin) out there still hacking up firewood for homeowners. The MS250 is still nice and light at 10lbs and pulls the 18" bar with authority.