I also like 10:1 odds.
The speed (effectiveness) depends on your troops. For example, Heavy Infantry are less effective so the bar goes down slowly, whereas Archers are better so they reduce the morale bar more quickly.
Even with 10:1 odds, storming can take awhile if, for example, they have 2000+ garrison/levies.
Storming tends to be more costly with troops but you can take over the holding more quickly, whereas sieging takes time. Depends on the war situation and whether you have time or whether you want to wrap things up quickly.
Besieging tends to save you more troops over time, but there are rare cases where several unfortunate events lead you to lose more troops than you would have if you had stormed.
Note that you can storm after you have started besieging - you do benefit from the decreased morale that you've already caused. However, every time you start a storm (click the button), the defenders do get a small morale boost (so if you quit and load a lot, then storming is NOT good!).
Besieging can benefit from a Siege Leader, but the latest patch's quirk of removing commanders can reduce the effectiveness of this. Ideally you will have a Siege Leader in your COURT (not as a vassal) so he isn't automatically removed. But if your siege leader is removed, then you need to move your army to reassign him, and that resets the 12-day counter.