Titanium Drill

The drill wins on raw speed, but it reaches a tile less far and it ignores every mining speed bonus you own. The moment you have a mining potion up, or armor and accessories feeding into mining speed, the Titanium Pickaxe pulls ahead and stays there. Take the drill for unbuffed digging and the pickaxe for anything you have prepared for.

It opens up nothing new. Everything this can break, the Mythril Drill or its counterpart could already break, so the bars you spend here are bars not going into armor or a weapon at the point in the game where that matters most. Build one after your gear is finished, or skip it entirely and wait for the drill that comes after the mechanical bosses.