In SG-1 and SG:A the stargates are made of a material that is nearly indestructible; it didn't seem certain that even a nuclear blast would destroy a stargate.
But in SG:U a stargate had a chunk blown out by a blast from a drone. The blast of a drone couldn't take out a weakened shield on Destiny, nor did it make a ginormous blast in the streets when one tried to kill the SG:U scouting teams in the second to last episode, so I doubt the blast was on par with a nuclear explosion.
So is there anyplace that canonically stated the gates created by the seedships were different or weaker than the gates made in the Pegasus and Milkyway, but still would have held up to centuries or possibly eons of erosion/weathering on a planet in the distant reaches of the universe? My only idea is that the gates are made of more "native" materials as the seedships are recharging supplies periodically, like Destiny refuels from stars.