I've had three washer dryers because there isn't any room for separates, so I don't have any experience of anything else.
My parents have just used into a rented place with a washer drier…it’s useless as a drier! Takes 3 hours to dry anything (luckily leccy is included in their rent). it’s an Indesit, an expensive Bosch or Miele might be better I guess.
I've never had separates to compare with, but my Indesit is singularly useless at drying compared with the two previous Hotpoints. I'm tempted to think it might be the 'Eco' design rather than the manufacturer though. The tumble isn't agitating the laundry well enough, so large stuff like sheets come out damp in the middle unless you break the cycle to readjust the load.
it's better to have separate machines due to reliability issues
Mine have been reliable: Hotpoint 9934 12 years, Hotpoint WD60 14 years, Indesit 7125 still going after 9 years.
Don't know why, but they use more water per wash than a washer.
The dryer uses water for the condenser.
They also "eat" electric. More than individual seperate washer and drier.
Has anyone else got an data for comparison?
Mine uses:
500Wh for a wash cycle (synthetics, 40C)
730Wh to dry 7 pairs of socks & pants
1500Wh to dry 2 double sheets & pillowcases.
Mine's grinding microfibres off the clothes when the previous ones didn't. I think it's because the Eco design is using enough water to make the clothes waterlogged and heavy, but not enough to hold them in suspension and make them weightless. I can see the way clothes are wearing out faster.