When do I conquer, when vassalize?

[Skoga]

It's hard to decide

[felmari]

how about vassalize all you can.

you can always integrate later.

[Ryika]

After the very early parts of the game, you should pretty much always vassalize even if you want the territory for yourself, since vassalizing and later integrating (via oppressive vassalization policy) is much more influence efficient than claiming and conquering, and as a bonus it skips the -20% happiness from conquest which can be a problem in some configurations. Claim their capital and any other easy to reach planets with lots of pops, and the rest can be integrated cheaply.

For permanent vassals, a good ballpark is to start by conquering/integrating your neighbors, and then when you've already got a large empire, that's when you start adding vassals.

This works well mostly because of how growth scaling works (with default settings), allowing a medium sized empire to grow more pops than a small one, while also not running into the wall where your growth nearly stops when you become too big.

Of course there are many potential strategies that can work if you play them sensibly, so experimenting with different approaches can always be fun.

[ScreamCon]

So its a balancing game. If you intend not to conquer said terrain turn to vassal. Vassaling can make harder to conquer but not really if said vassals are in alliance with war controls.

Vassals can lead to scenario where your ships have to go through friend space to reach your other owned sectors. Strong diplomacy builds should have you covered.

[MP]

Why vassalize when you can eat?

[HappySack]

Why not both? vassalize everyone but steal some territory if it's practical.

[Jarlaf]

Personally, with my most common play style I'll tend to claim and conquer in the early game to make sure I have enough planets to support what I'll need to run my empire in the late game. Usually 2-3 sectors maybe 15 core planets (which is really more then needed) Once that's secured I pretty much vassalize anything else, with the tenancy to turn them into Scholariums

[Cinnamoon_dragon]

You vassalize, when you don't want to deal with 25+ new planets and their social issues, but haven't built the Colossus yet.