Most amplifier circuits are basically the same, doesn't really matter who makes them. Just depends on what the purpose is (class) and what you happen to have laying around (or can get).
There is a huge possible difference in how a circuit is laid out on a board, how it's assembled. Some are more 'simple' than others, easier to build, sort of. Maybe not as many 'extras' included in the total design.
Some of those 'extras' ought to be considered as being 'standard', or used in/on all amplifiers. Like filtering, protection circuits, etc, etc (personal opinion). And then, some of those 'extras' are of the "Why did they do that!" sort of thingy.
All them people start with the same basic circuit, maybe add a little or leave out a little, then call it their "own" design. Anything 'wrong' with that? Not really, but there's nothing all that 'right' about it either...
- 'Doc