End of day the decision is yours but here is a few things to think of:
Yes LGW is a friendly base to be in as it is always changing, crew are friendly and most do like to party when they can. We also do get worked alot harder than LHR and sometimes you are treated as an outsider within BA. However, with the changes coming into LGW with Eurofleet taking over the Longhaul operation @ LGW
to become Onefleet (and it will happen) so you will be working on 737-500/300/400 - which offers both Club Europe and Eurotraveller and you will also be trained on 777 and possibly be First Class trained. while also working in Club World , World Traveller + and World Traveller. With Eurofleet LGW not being treated as Mainline even though your on a BA PLC Contract nobody can transfer into EF LGW from another base or Fleet and promotion done within the fleet(at the moment) . However, if you do accept LGW and the Recruitment team say
"You can transfer into EF LHR or any mainline fleet after 6 months, you must get it in writing as crew have previously been mislead"as their is only a Gentlemans agreement to transfer 54 per year to EF LHR . Im sure you will make a good decision that suits you !! Hopefully see you online soon at LGW !!