Is it because you risk less because them 3betting is far more likely cause of smaller SPR?

Thanks

When your goal is to steal the blinds, you want to risk the smallest amount that would reasonably accomplish that goal. When your goal is to get calls, you'll want to make it the same size so it looks like you're just trying to steal the blinds.

This is normally determined by the players I'm around more than the stack depths. If we are 100bb deep and they'll all fold to a min-raise, I'm going to min-raise.

If I'm getting called too frequently, I'll increase my sizing. If someone is 3betting me constantly I'll adjust my opening range, not my sizing. If I'm not getting called often, I'll start experimenting with a lower sizing.

One of the reasons is you can play more hands.
For e.g. if you introduce a limping range, you can play more hands than if you only play rfi.

In limit poker we are playing to win bets.

In no-limit poker we are playing to win stacks. At every point in the hand the strategy has to take into account the underlying threat to the players respective stacks. When the effective stack begins to shrink it is much easier to get stacks in, and consequently bet sizes shrink too, because a smaller bet still has the effect of threatening your opponent’s stack by the end of the hand.

I don’t change my opening sizes when my stack gets between 20-30 bbs. It’s the same as when stacks are 70bbs. Maybe once it gets to 80bbs, and definitely gets a little bigger at 100bbs, but not significantly. Based on the responses so far I might be in the minority.

I might change my opening sizes based on who’s in the blinds and what my hand is.

It's not ok to not change your or sizing 20 to 70bb, IMO. I mean when you are so deep it's imperative to make it bigger.

When we minraise with 20 to 30 bb's a 3-bet of 3x will take it to 6bb which we can call with much of our range. And that would be about 20% to 30% of the effective stack size (assuming our opponents have more).

If we raised to 2.5x a 3-bet of 3x would be to 7.5 bb's which would be 25% to 35% of the effective stack size. That would be reasonable with a 30 bb effective stack but not with 20 bb (at 35% the 3 bet would much more likely be all in). But still it would end up restricting post flop play at some point.

If we raised to 3x then a 3-bet would be to 9x and would likely would be a shove even at 30 bb effective stack.

So, we get to play post flop more which can be especially important vs either or both the blinds in position.

Similarly when we min raise we can do some things post flop that would be suspect if we hadn't min raised (e.g., on the turn our only choice would be to shove or check).

The other thing that comes up for me is that when there are one or more smaller stacks there is a chance they will shove no matter what our bet size. So if we don't have a hand we want to defend with, we get to save some chips. If we are happy to get it in, our bet sizing won't matter.

For me I go with 2.1x (rounding down) from 15 to 27 bb's, 2.25x (rounding up) from 27 to 40 bb's, 2.5x from 40 to 100 bb's and 3x over 100 bb's.

I do expect my raises at <= 20 bb's effective will generate 3-bet all-ins anyway. And some players like myself will 3-bet shove <= 25 bb's no matter the original raise size.

technically with 25-30bb stacks aren't we either 4bet jamming or folding? calling 3bets with a massive range disadvantage oop doesn't sound fun. Also if you get 3bet by someone oop they're probably making it 4x.

the reason for rfi sizing of 2.0-2.2 is we're playing to pick up blinds and antes. Going a little deeper we can think about it like this: i'd rather open 2x faced with a jam, i'd rather open 2x faced with wider ranged oop calls from blinds, i'd rather open 2x faced with any kind of 3bet, i'd rather open 2x faced with folds. Putting it like this it's easy to see it's the best strategy.

Keeping pots small also deters a lot of spazzy bluff plays from maniacs which can be seen as a positive and a negative at 25bb. Opening 2.5x a spazzy player in the blinds is way more likely to fight you postflop and put you in shitty situations. Being forced to play for stacks with a flopped top/mid pair vs check raise flop, turn shove by a maniac isn't fun with very little info. Smaller preflop sizing tend keep this kind of player more honest post flop as there's less gain.

Thing is we may not be oop if the 3-bettor is the SB or BB. So there are times when I just call the 3-bet in position with 25 to 30 bb's to maintain positional advantage.

I have found that <=3x 3-bets from SB or BB oop happens at least half the time (live). For whatever reason a lot of people don't take their position into account when 3-betting, or they get scared about bloating the pot oop, or they are trying to lure players in with AA/KK. But yes when the opponent is a really good player (or me) it will be at least 4x.
A pre-flop raise of 2x is much less likely of picking up the blinds than one of 2.5x or even 2.25x (and according to Greg Raymer even 2.1x gets folds a lot more than 2x raises)

Personally I call wider when in the BB against a raise of 2x vs 2.5x