personally i wouldnt bother for a short-ish 6hr flight. you may be better (depending on when you're travelling) booking economy and then paying to choose your seat.

you get the same [rubbish] food and service in WT+ as economy, same luggage allowance and same boarding privilege (cattle scrum) seat is a bit wider with a larger pitch (see the ultimate BA guide or seatguru.com)

however it really depends on the price difference.

PS> thats rubbish food - not rubbish service...service is intermittent - sometimes good, sometimes bad.