Regioselectivity in Electrophilic Aromatic Substitution of Pyrrole and Indole
The traditional explanation for the reactivity of indole at C–3 is that attack at C–3 does not disrupt the aromaticity of the benzene ring in the cationic intermediate (see any organic chemistry book; for heterocycles a good book is Joule and Mills as has been suggested in the comments):

You have drawn many of the resonance structures for the intermediate, including the two shown above. So I should mention that the major resonance contributor should be the one where the positive charge is borne by the nitrogen. In this case, the positively charged nitrogen has four bonds and a complete octet; whereas if the positive charge is on carbon, that's formally a six-electron, electron-deficient carbocation. Many thanks to Buttonwood for pointing this out.
To a first approximation, one could consider the reactivity of indole to be as if it were a benzene ring plus an enamine, and enamines are very, very happy to react β to nitrogen and not α. This is of course not an enamine, but the idea is the same.
For pyrrole, there is no &quot;other benzene ring&quot; to worry about, so this consideration does not apply.