Why the small raise sizes at 2/5

Because 2/5 players are marginally better than 1/3 players on average, so more people are aware that without very opponent specific reasoning, opening to 5bb+ is suboptimal

Because the other players are better. This matters for two reasons:

A) You are more likely to get 3bet when you open. Getting 3bet when you open 5x sucks because you can’t defend as often (big raise, low SPR) and because you lose a lot of blinds when you fold.

B) Players are much less likely to make calling mistakes pre-flop facing large raise sizes compared with at $1/$2. At $1/$2, players will call 5x with dominated hands like QJo and 75s. At $2/$5 many players know to fold these hands.

If you are playing at an exceptionally soft $2/$5 game, there is nothing wrong with opening to $25. But that shouldn’t be the default.

I don't know about your room, but where I play, the rake at 2/5 is basically the same as it is at 1/3, so it makes more sense to raise to a large size at 1/3, and less sense to use the same BB multiple at 2/5.

Also, the stack depth tends to be different enough to warrant consideration. The BI in my 1/3 game is $100-$500, and you see a lot of short stacks. The BI at 2/5 is $200 to $1k, and you don't see as many short stacks.

The net effect is that a lot of 4B's at 1/3 tend to just be all-in jams, whereas at 2/5, you see more 4B pots with money behind going to the flop. At 1/3, it's like $15, $50, all in for $300. At 2/5, it's $20, $60, $150, and we're going to the flop with $700 or more behind.

Lastly, even though the 2/5 pool isn't THAT much better than the 1/3 pool, the 1/3 pool does have a lot more beginning players who don't know enough to understand how position affects opening ranges. The typical 1/3 rec doesn't understand that a UTG open to $15 isn't the same as a $15 open from the HJ. At 2/5, that UTG open is likely to be seen as stronger than a HJ open.

The 1/3 crowd will compensate by varying their raise sizes more than the 2/5 crowd. A 1/3 rec will be more likely to have sizing tells than a 2/5 reg.

Also, agree with what the Dan and Dilly said - as you move up in stakes, the pool tends to make fewer mistakes facing larger bet sizes.

Some correct info in the replies.

However, keep an open mind.

Whenever I move up I think the Vs will all be crushers who call my bluffs with Q high because my nostrils flared when I bet.

It might vary by area but there are very few people at 2/5 who are all that good. Even many of the winners will be staring at their phones the whole time playing a pretty rote strat and might not adjust to you.

Anyone who uses totally uniform sizing is probably not that good. Sometimes the table is all recs and you can adjust your sizing accordingly. Some people will limp call or raise call almost any amount. So do the obvious thing.

If you are new to the table and people don't recognize you you don't have to worry about being consistent with the past.

As a rule $15 is too small imo as I want to play bigger and beat the rake. But when you're moving up, you might want to keep it smaller so smaller raises can be the way to go.

Think through each situation and have good reasons for whatever you decide.

I would say in theory if you are a winning player you would make more opening larger then smaller at any stake - rake becomes less of a factor, the average pot size is larger, you should be netting more bb/hr. The only argument I could see to this theory not working is if your opponents pick up on this and start 3bing you wider, although you can counter that by 4bing wider. Probably the ideal strategy is to have exploitative sizings based on your opponents, position, etc. At live 1/2,2/5 and some 5/10 games playing exploitative is where the money is made.