montydruitt said:
The thing is, the 'name' on the bike is the name of the assembler, but all of these bikes are made of collections of parts from relatively few sources; the frame is the biggest and most obvious but it's far from the most important.
Really, you'd be better looking at it this way. There are three makers of bicycles in the world: Campagnolo, Shimano, and SRAM. OK, they don't make the bicycles - but they make the parts of the bicycles which make the bicycles significantly different from one another, and there's more difference between (say) a Cannondale bike with a Shimano groupset and identically the same bike with a Campagnolo groupset than there is between a Cannondale and a Specialized with the same groupset.
Having got that far, Shimano are like General Motors. They are a mass market maker; they provide a very wide range of models at a very wide range of price points. Some of it is rubbish, most of it is OK but none of it is very good.
SRAM are like Volkswagen: they too are a mass market maker, but they're engineering-led and they aren't competing at the cheap end of the marketplace. All their kit is at least OK and some of it is very good.
Campagnolo are like Ferrari. They only make racing equipment. Their cheapest stuff is good (but expensive); their best stuff is the best there is (but scarily expensive).
My advice? Don't buy a Vauxhall.