Gg. I travel frequently out of LGW and LHR to the same destination. The LGW crews are not as good on this route. You hear things like "there is only three of us sir", "I can't get it now as we haven't got time"......
As for longhaul, well it was not that great at the start and for many months after. Hopefully after three years peope know what they are doing. I have not flown longhaul out of LGW, but I have heard that the crews work very hard to achieve a fine service.
The main difference is that the SFG was a holding pool for LHR, what will happen to morale if there is no chance to transfer?. Crew at LHR want to be there and it shows in the service.