While reading A Storm of Swords and A Clash of Kings I got to thinking of how Tyrion in many ways reminds me of Lois McMaster Bujold’s Miles Vorkosigan. And I noted that the patriarchal and martial-minded society of Westeros wasn’t too far off from the harsh and militaristic society of Bujold’s Barrayar. Tyrion’s mother is often hinted at being one of the few people to get through Tywin’s hard outer shell much like how Cordelia Naismith was in some ways a softening influence on Aral Vorkosigan.
Miles and Tyrion are both quick-witted and intelligent and looked down upon by societies that value physical prowess over mental acuity. Both overcome their infirmities and manage to participate in battles of various kinds (Miles as Admiral Naismith, Tyrion in the defense of Kings Landing) and both suffer a debilitating secondary injury that increases their physical frailty and/or deformity (Tyrion in the defense of Kings Landing and Miles is almost killed and suffers from seizures as a result of his cryofreezing).
Both characters offer up interesting examinations of the nature versus nurture discussion but I think in both cases either side of the argument might prove viable. As my brain drew the links between these characters I had to wonder that if Joanna Lannister had survived his son’s birth who or what her son Tyrion might become. Tywin is an interesting character in and of himself and several characters comment on his feelings regarding his wife over the course of the series and you might wonder at the kind of father he might have been with his wife at his side. I’m sure it wouldn’t have been all sunshine and roses, this is George R. R. Martin we’re talking about here, but it is an interesting thought. I think both Tyrion and Miles are products of their environments both in regards to the world they inhabit and the people that surround them.
They aren’t quite two sides to the same coin but they are about as close two characters in different genres can be.
King of the Nerds!!! 
Tywin Lannister, to me, seems a hateful man, changed for the worst ever since Joanna died. He seemed to truly love her, and the fact that Tyrion killed her (through no intent of his own) destroyed any possibility of love to survive for Tyrion from Tywin. Yet, we do not know how ‘changed’ his ability to love and nurture has been. It is possible Tywin, regardless of Joanna’s death, would have frowned upon his son and shown little love because of his disability. I believe this is most likely. Even more importantly, society would still ridicule him for his appearance. Therefore, either way Tyrion would have had to hone his intellect to gain power and acknowledgement, but might have had less empathy for bastards and the like if he had been loved. Ah, the beauty of speculation! Great, thoughtful post!
Another similarity….both have fast-talked mercenaries into coming over to their side.
For me, the biggest similarity between Miles and Tyrion is the hunger for recognition. And the big mouth. 😀