I've had both the Tado and a Wiser thus can compare the differences:
Tado
Internet based schedules, thus if Internet fails the schedules also fail and any ch/hc will need to be turned on manually on the smart thermostat
The schedules come on at a delayed time after the scheduled set time, although this is random amongst owners.
The relays in some wireless receivers can be icky and need a clout to work, again there only seems to be some faulty ones.
The srv's are widely optimistic with the room temperatures.
However it is fairly sophisticated in the app's setup compared to the on/off srv's of the wiser setup.
I'm getting random battery low notifications from one srv when the batteries are fine.
It has no range extenders, so if you live in a large property then the srv's might lose their connection.
No smart plugs.
Support is poor.
Wiser
Hub has a weak wifi connection.
Srv's can be noisy.
Basic system compared to the Tado, but that can make it easier to use.
Schedules continue to work even when the internet goes down.
There are override buttons on the hub that can boost the ch or hw which are easier to use.
They have smart plugs which act as range extenders for the srv's.
Support is better.
If I could do it again I'd chose the wiser over the tado but the Tado starter kits are cheaper at under £100.