I have frequently hear casters talk about how Roaches have replaced Hydralisks in the mid game. In what ways have roaches replaced hydras? Isn't the DPS and range on a Hydra considerably better?
While it is true that the range 5 (or 6 after upgrading) is better than the roaches' range of 4, and that the DPS is considerably better (~14.5 vs 8 DPS), the roaches still have a number of advantages over hydras.
- Better Health: 145 vs 80
- Better Base Armor: 1 vs 0
- Better Speed post-upgrade: 3.0 vs 2.25
- Lower Cost: 75M 25G vs 100M 50G
- Faster Build Time: 27 seconds vs 33 seconds
- After upgrades, can move while burrowed.
Probably because Roaches:
- are cheaper;
- don't require a Lair, so you get access to them earlier;
- can move while burrowed (requires Burrow);
- heal themselves while burrowed (if upgraded);
- run faster while not on creep (if upgraded).