With you being BA Gold I would go the direct route....you'll earn a tidy some of Avios and your status will help you pick a decent seat in Y with plenty of leg room. At least one way is during the day so not exactly a tortuous journey.
Getting upgraded is very much route dependant but the way BA are filling up their aircraft down the back your chances are better than they used to be.....always a gamble though and seems to happen more when travelling in WT+.
I suppose it all boils down to the convenience of flying direct over guaranteed comfort and whether you need the Avios or not.