Where is the better loot?

In the higher-tier breaches you unlock from Greylock (the central hub).

• The deeper the tier, the better the loot: modules roll more ports and higher modifier tiers, and rarer rarities turn up more often. Stratum 0, the tutorial tier, cannot drop Regalia.
• Beta Patch 1 improved Prototype odds in tiers 3 to 7.
• Dark Triton, a rare recipe mineral, is found in the breaches off Greylock.
• To open a deeper tier, extract from the one before it.
• From Stratum 3 up, tiers also have a minimum build rating: 6,000 for Stratum 3, 8,000 for Stratum 4, up to 16,000 for Deep Strata. A bare Standard Seraph rates 2,200, so plan a bigger build.