I voted Inner Focus for a few reasons.
1. It's less limiting as to which art design we chose. Even though lightningrod and volt absorb are somewhat similar, i prefer to choose an ability which limits even less, since as some people have alluded to previously, it does effect some designs. Inner Focus has zero design elements to worry about. More flexibility in art > Less, even if this is a slight advantage.
2. It still has some use in being a perfect partner. Being able to take flinch is helpful in a similar vein (although to a vastly inferior degree) to volt absorb. Often times, and especially now that togekiss usage will be on the rise after this CAP, paralysis is accompanied by flinching. While I agree that it's a small benefit at best, being able to avoid being flinched means less flinch-hax and makes him at least somewhat able to take an attack that would flinch. Some functionality > No functionality.
3. Both of these abilities suck. Inner focus doesn't help much at all, since this pokemon's defenses aren't exactly amazing and there aren't that many flinching moves used. Out of the main pokemon which use flinching moves (fake out users, togekiss, jirachi, and gyarados), this pokemon already outspeeds all of these bar fake-out users (it's priority) should they not be using a scarf/gyara has a dd. If they do, air slash is super effective. Jirachi's dealing much more damage with iron head than this pokemon wants, and gyarados already should ohko (i haven't done the calcs, but I'd be surprised if he didnt). So this pretty much only helps against fake out. Neither Inner Focus nor Lightningrod warrant much use, anyway, so there is no reason to reject inner focus for not following through with the purpose of this CAP. If anything, lightningrod does literally nothing to help togekiss; so much for a perfect partner.
Please prove to me why lightningrod is uniquely better than inner focus, because there have been 0 compelling arguments to support that claim.