SuperMeep You're wrong on several accounts, and this last post actually made your arguments worse. Purely as a special wall, Latias is the superior Pokemon.
-First off, Speed matters on a defensive Pokemon. If you don't understand this, you clearly haven't been playing the game long enough. For those of us who have played long enough to appreciate the natural Speed on Pokemon such as Deoxys-D, Jirachi, Latias, Celebi, and Landorus-T, we know that good Speed can be the difference that makes a good defensive mon great. Especially when--
-Latias has recovery in both Roost and Wish. This alone makes it superior in a walling role, and its Speed makes it that much better at abusing recovery.
-Latias' support movepool includes Defog, double screens, Roar (far more reliable than D. Tail this gen), Wish, Healing Wish (though this is not too good on the defensive sets) and Thunder Wave. Goodra's support move pool is almost non-existent, containing nothing that you couldn't find on just about any Pokemon.
-Gooey is irrelevant in fighting Special attackers, so it's irrelevant to Special walling. Sap Sipper is nice because it grants immunity to powder attacks (honestly, what Latias/Goodra cares about special grass attacks?), but the only common user of them in OU is Breloom-- a physical attacker.
-Levitate on the other hand is an incredible ability for a defensive Pokemon because it makes you immune to spikes/toxic spikes, giving you incredible survivability with SR as the only hazard that hits you (and only neutrally)
-Neither Latias nor Goodra, after investing in Special bulk, are going to be beaten by the vast majority of Special attackers, so its extra bulk there is useless.
-Sludge Wave is totally irrelevant, because the best Fairies in OU are either immune to it (Steel/Fairy), or are hit by Thunderbolt as in Azumarril and Togekiss.
Purely as a wall to switch into special attackers and support the team (the role of a special wall), Latias is the superior Pokemon.
Goodra does have some use over Latias as an offensive tank (not as a special wall), but its strength over Latias is almost exclusively related to what it lacks, rather than what it possesses. The only reason why you'd ever think of using Goodra over Latias is because of the weaknesses Goodra lacks.
-No weakness to Ghost makes handling Gengar/Alakazam a lot easier.
-No Pursuit Weakness to be one shot by Tyranitar
-No U-Turn weakness to be one shot by Genesect (and it does have fire attacks besides HP Fire, so another point for Goodra there)
That said, while it does make Goodra a bit better suited to handle certain situations, it's still not particularly GOOD in those situations. Goodra does not want to be taking repeated STAB attacks from Alakazam or Gengar (and unlike Latias, it lacks a Psychic resist so it's destroyed by Psyshock). Even without a Pursuit Weakness, Tyranitar and Scizor can still do massive damage to it with Pursuit, so it still has to be careful (especially since it has no recovery). U-Turn from Scizor/Genesect doesn't one shot Goodra, but it'll still leave massive dents when the enemies have +1 or Choice Band. Needless to say, despite Genesect being a special attacker, neither Latias nor Goodra wants to try to switch into it without knowing it's choice locked into a Special move not named Ice Beam.
To be clear, in the bigger picture, Latias is not a very good Pokemon in this meta. Likewise, Goodra is also an extremely overrated Pokemon, and not really "good" in any sense.