Pollymagou, it is very much up to the individual. WW generally pays more purely because you are away more. That said, you are paid allowances in local currency. On EF a lot of your allowances are in Euros. A lot of WW allowances are paid in US Dollars - not so great at the moment.
On EF, you have control of your life due to preferential bidding. If you want to, you can be home every night. On WW you get to travel but then there is jetlag to consider. Also for every favoured destination (eg SFO), there are the more "challenging" trips (LOS, ISB, TLV) which can be very draining.
One thing to remember is that there is the ability to request to transfer between either fleet after two years. It may take a while to come through but ultimately, you have the chance to try each fleet over a number of years and see what works better for you and your circumstances at the time.