Palladium Waraxe

At this tier both options fell the same trees. The difference is how they handle. The axe swings, so it covers an arc, times cleanly against a trunk, and doubles as a panic weapon if something wanders into you halfway through a harvest. The chainsaw runs while you hold the button, which is smoother for flattening a whole grove but locks you into doing that and nothing else.

Neither is a long term tool. The next Hardmode ore tier beats it, and those tiers come around quickly once altars start breaking. Put your bars into the pickaxe side first, since mining speed gates how fast you progress and chopping speed only gates how fast you get wood.

The choice between this and the Cobalt version is not one you make. A world carries one of those two ores, and you build whichever your altars gave you.