Analog quantum computers (like annealers) are simpler to make, and they have a lot more play w.r.t. their building blocks when trying to make interesting effects... but ultimately they are limited by noise. Digital quantum computers restrict themselves to finite gate sets, often requiring expensive decompositions to do basic operations (e.g. [1]), but those gates are compatible with error correction so noise can be suppressed arbitrarily (e.g. [2]). It's very similar to how an analog classical computer can do addition with two resistors and a junction, but the accuracy is limited by the precision of the resistance. Whereas a digital classical computer will decompose the addition problem into bits and gain more precision by adding bits so that increasing precision becomes about increasing quantity instead of quality.