A colleague has the DWS774 and so I've had the chance to try it against the DW777 I use on a daily basis at the moment. It shares a lot of the same design philosopy, but is smaller, lighter and very, very portable. In terms of power, noise and accuracy I don't think there's much between the older saw and the new one, although the 777 is slightly better on hardwoods. Dust extraction isn't stellar, but to get good DX you really do need to go to a Festool Kapex. Certainly appears to be a good general purpose site saw with sufficient capacity for most second fix tasks and a fair bit of first fix carpentry (e.g. stud walling, etc). even though the saw lacks and facilities for double bevel cutting (handy but not essential) and has no trenching capability (which is sometimes very handy), although I can live without both especially at a tad over £200
Can't say I've ever seen the Bosch other than in a showroom. It is certainly is a lot bigger.
It depends on your own preferences, but I can say that in the last twenty years I can recall seeing many deWalt and Makita mitre saws in use on sites (the two favoured brands), together with a smattering of Elektra-Beckum/Metabo and Hitachi saws, the occasional Festool (other than my own) and recently one or two Milwaukees. Never seen a Bosch - even on jobs in Germany. I'm talking about user-owned tools BTW, although hire shop saws also tend to be deWalt, Makita or Milwaukee. Surely that speaks volumes in terms of quality of product?