To begin with, we must establish the parameters of our study. For the sake of clarity, we must consider the 'Double Nerd' (i.e. he who indulges in both comic books and Dungeons and Dragons) out of scope. I appreciate that this is likely to create a skewed result but the water-muddying effect of the Double Nerd is practically impossible to negotiate other than by circumventing it entirely. Then, there is the matter of gender. To avoid constant he/she, him/her, his/hers, we must assume our nerds are male, at least for the sake of this study. It is of course a known fact that some females read comic books and play Dungeons and Dragons, but we cannot technically label them 'nerds'. They are, instead, to be considered 'culturally adventurous and non-prejudiced'.
Attribute 1: Physical Strength
First let us compare the physical strength of our subjects. We will begin with the Comic-Book Nerd. Bodily, the Comic-Book Nerd may be variously tall, short, slim or overweight; he is, however, unlikely to be, in any true sense, 'muscled'. This lack of significant musculature is as a result of the delicate handling required by comic books, particularly rare comic books. If someone of jock or beefcake proportions were to pick up, say, issue eleven of 'The Avengers' (“Co-starring Spider-Man -- 'Nuff Said!”), it would be rendered into something resembling confetti within minutes, a victim of hands made for grasping sports equipment and excessive 'high-fiving'.
The Dungeons-and-Dragons Nerd, whilst as likely to be tall, short, thin or overweight, may be possessed of a certain amount of 'beef'. The Dungeons-and-Dragons Nerd handles the materials of his obsessive hobby with considerably less in the way of care. In fact, it is a badge of honour amongst these individuals to be the possessor of the most battered, torn and coffee-stained edition of 'The Monster Manual'. Also, it is not uncommon for a participant in a Dungeons and Dragons session to leap up during some imaginary combat, seize the nearest sword-like object (a ruler, umbrella or an entirely non-existent 'air sword') and wave it about with considerable enthusiasm. This activity constitutes exercise and can result in the building and/or toning of muscle. In terms of physical strength, it's one point to the Dungeons-and-Dragons Nerd.
Attribute 2: Speed
For the sake of argument, we must compare Nerds of similar build. It is true that all Nerds are fast. It is necessary for their survival. School, college, university or even the work place can be a dangerous arena once a copy of 'Justice League of America' or 'Deities and Demigods' is discovered in ones possession. However, it is undeniable that the Dungeons-and-Dragons Nerd is, by far, considered to be the most socially-unacceptable; their conscious immersion into another world is seen by mainstream society as a form of retreat from the real world, a kind of cowardice, and this, like nothing else, brings out the bully in the ordinary man or woman. Therefore, the Dungeons-and-Dragons Nerd is, by necessity, the faster. Another point to them.
Attribute 3: Combat Prowess
This is something of a moot point as, by definition, Nerds can't fight. But we must consider them on their own terms. The Comic-Book Nerd's combat ability is derived from hours of studying the fighting techniques of Batman, Black Panther, Daredevil and the likes. As a result, he will have developed a completely inaccurate notion of where the body's various nerve points are to be located. Thinking a simple finger-jab to a spot just beneath their opponent's left nipple will render them paralysed and helpless for two and half hours, the Comic-Book Nerd enters into combat utterly unprepared for the reality of a really hard slap to the ear. The Dungeons-and-Dragons Nerd, however, has, in his own mind at least, 'lived through battle'. The techniques he will bring to bear, though crude and ridiculous, will be enough to send the Comic-Book Nerd into a scurrying retreat. Final point to the Dungeons-and-Dragons Nerd.
We can only conclude from our study that if ever there is a confrontation between a Comic-Book Nerd and a Dungeons-and-Dragons Nerd, the Comic-Book Nerd will be roundly and humiliatingly defeated. Both, however, are likely to be seen a source of considerable amusement to anyone witnessing the resulting melee. It's probably for the best if Nerds can just learn to get along.