It could just be a power difference. If wandless magic came with no penalties attached, you'd have to be mad to continue to use wands if you can manage wandless magic like Dumbledore can. It strictly dominates wands - you can't be disarmed nearly as easily. (And when we see wizarding children 'naturally' use wandless magic, isn't it weaker than what they can manage with wands?)
A big enough difference of degree can look like a difference of kind.
Two things, one: being more difficult to disarm isn't really as much of an advantage as it might seem. Remember, we have some idea of how magical combat works in MoR, and it seems to revolve around layers of active and passive defenses - during Bahry One-Hand, veteran Auror, v. Polyjuiced!Quirrel, the description went
...According to the Defense Professor, the essential art of dueling consisted of trying to put up defenses that would block whatever someone was likely to throw at you, while trying in turn to attack in ways that were likely to go past their cu
(The HPMOR discussion thread after this one is here.)
The previous thread is over the 500-comment threshold, so let's start a new Harry Potter and the Methods of Rationality discussion thread. This is the place to discuss Eliezer Yudkowsky's Harry Potter fanfic and anything related to it. The latest chapter as of 09/09/2011 is Ch. 77.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight. The fanfiction.net author page is the central location for information about updates and links to HPMOR-related goodies, and AdeleneDawner has kept an archive of Author's Notes.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: