The definition for SUTO and WUTO is the following:
If some process TODelivers some message m before message mʹ, then a process TODelivers mʹonly after it has TODelivered m.
And for WUTO
If process p and process q both TODdeliver messages m and mʹ, then p TODelivers m before mʹ if and only if q TODdelivers m before mʹ.
I have a hard time getting my head around this. For me, both of them sounds the same...