The 379s are a fundamentally decent train and inherently suitable for GN. As ever, the implementation has been a mess, partly because politicians allowed them to be stored for too long, and partly because no one wants to pay to have the trains reconfigured to alter them from an airport express spec to an outer suburban one. For the end user, this manifests itself in poor availability / reliability (thankfully seems to be improving now, but in their early days it was atticious) and niggles like too much first class, lots of broken window locks (not sure why this should be the case, 387s generally don’t have this issue), etc etc.
What is slightly ironic is that the 387 is essentially the superior train, simply as it’s a later generation of Electrostar (and the 387 build quality does see noticeably better), yet is being somewhat relegated to stopping work as a rump fleet.
Incidentally, can anyone comment as to whether 387s and 379s have the same traction package, or whether there is a difference? I can’t decide if the traction motors sound the same or not, the 387s seem to have a slightly more distinctive whine to them.