Accuracy is probably equal. You need an operator who knows how to use it, but once you do they can accurately do calculations.

As for practicality, I've seen abacuses...abaci? Abaca? Abacapodes? range in size from ~a textbook to ~a smart phone. In basically any case you can hold one in one hand and manipulate it in the other. Some rods, some beads and a frame, you could improvise an abacus pretty easily. There are different implementations of abaceaux but you can usually add, subtract, multiply (and thus do exponents), divide, square root and cube root. With a simple to build, easily portable device.

His machine, at a glance, reminds me of a Babbage difference engine. It's the size of a steamer trunk and is full of gears, chains, wheels and linkages. Looks complicated to build and impossible to improvise, though it might be easier to train someone how to use it. The method of operation reminds me a little bit of a Curta calculator, which has a similar "put your numbers in with sliders and then turn the crank to math them" interface, but a Curta is half the size of a beer can. Intricate and expensive but functional.