Different areas feature different events, encounters and nodes.
- Nebulas will have approx 3+ nodes that are NOT sensor-disrupting nebulas.
- Homeworlds feature specific events that allow you to unlock some ships.
- Pirate sector got plenty of pirates (totally unpredictable)
- Race-controlled sectors will mostly have that race pilots (good luck boarding a Mantis crew of 5)
Although it's randomized, it doesn't take a load of thought to know what you'll find. Zoltan sector = loads of Zoltan = easy to teleport in and slay em. Rock sector = loads of stoners = teleport in, kite them around the ship, breaking their systems (they're too slow to ketchup)
TL;DR: Yes, there is a differense between regions, and red regions have more hostile encounters than green ones.