There's two basic problems with a washer dryer idea...
1. There's not enough space in the drum to tumble dry clothing effectively as well as there not being enough ventilation (so the water stays in on wash) to allow good airflow. And this does apply to so called large capacity ones as well.
2. There's a LOT
more packed into the same space and, as you up the load size, you decrease the available space.
Number one means that the dryer is woefully inefficient and, I do mean woefully
Think on the electricity used in a normal dryer then double or treble it and you're close to the mark. Then, as it has less airflow, the dryer takes ages so to hours or more to dry a pair of jeans (if it doesn't burn them) is not unusual at all. You'd almost be as quick hanging them over a radiator.
Meanwhile number two means, loads more to go wrong, clog up and break in general.
Now, washer dryers for we repairers are a mixed blessing. On the one hand they break more so, it's good for business and as they are more expensive people pay to get them repaired even if they are a heap of, errr, "rubbish".
On the other hand we tend to be an honest bunch in the main so we're telling you before you buy one, they're rubbish and they don't work well and they cost more and they need fixed more.
Now you have more info if you really, really still have to buy one although I'd rather buy a clothes horse as that won't break...
Miele is the best machine but you'll need a mortgage to fix it when it breaks and, while it's better than the rest, it'll still break.
Bosch, best balance probably.
Siemens, Bosch with a different badge on the front.
No washer dryer, best buy.