There's just a stock equation that goes something like:
Gomez = more solid.
Barca = great at attacking.
Therefore we must play Gomez against Barca.
Personally, I'd say the best way to beat Barca is to prevent their attackers getting on the ball, by pressing high, by shutting down Barca's passing at source. I'd rather have TAA and his recovery skill plus attacking nous for that job.
I was about to reply to Yorky but then saw you had already done it.
Gomez, as much as I rate him as a defender, benefits from a sort of reverse Glen Johnson assumption/rule.
People saw how good Johnson was going forwards, so assumed he was incapable of defending well (which in a more conservative role for England he often did quite well). Therefore he was our attacking defender.
With Gomez they see that he is clearly not able to contribute as well as TAA in an attacking capacity (which really is no disrespect, given TAA's class). So the same reductionists assume he is therefore a better defensive defender.
For as highly as I and we obviously rate him at centre back, I actually don't think he's a better defender at right back than TAA (physical strength aside). Firstly, as we've seen this season having great attacking fullbacks is a great form of defence. Cardiff's wide players scarcely entered our half. Secondly, TAA is much more switched on to covering the centre back than people realise, he has great proactive defensive instincts.