Actually that job is ideal for a chain saw. But the same rule applies as the one's we're recommending for the sawsall. You need a good/right blade. It never fails to amuse me when I see someone failing miserably with a cutting type tool. And you look and the "pack" of blades cost $3 for a 12 pack! People expect performance from bargain priced junk. Time to go back to school. Good blades are expensive. The only saving grace is the expensive brand name ones work like crazy.
With a chain saw, you need a quality chain. No, not discount store junk, go to a Stihl dealer and buy or have them order you a carbide chain (carbide cutters) or a hard chrome model. Those are usually used by fire departments or professional cutters who know what they're doing. You can, too. Then when you're done with the part of the project that requires them, change back to other chain.
With the Sawzall, buy a big brand blade and again, only use it when needed. Sure, its easier to just continue and maybe ruin a big dollar ($10) blade, but then you won't have it when you need it. Once at a tool booth at a local flea market there was a small barrel full of blades. The sign said $1 each. The other guys there were pulling out the packs of a half dozen, thinking they were getting the bargain. I selected the Remington "Grit Edge" blades. I took home 10 of them and I'm a happy camper. They abrade, chew, their way along. Slow but hardened steel is just lunch to them. I still have 5 or 6 and its been years now.
Spend the money and buy quality. It will pay you back in faster work and less hassle in the long run. Oh, you could say that about guns, too. Buy the best, its only barely good enough.