Recently done some study on when to have a Merged range vs a Polarized one pre flop. I was wondering a lot about this and after watching a video RunItOnce and doing some work in some poker software programs and this is what I gathered. Just thought I would share this info as I think It is useful and also pretty interesting. If you have a RunItOnce account watching the video on this is probably better than reading my post but this will be my summary for people that don't have an account there.
First note is these situations are generally going to apply more to when you are playing against better players
The very basic summary is you want to have a polarized range in a spot where you want to be flatting a fair amount of hands and you want to have a merged range in a spot where you will pretty much be raising or folding.
The reason for this is when you used a merged range you just 3 bet say the top 10% of hands rather then a polarized range where you 3 bet maybe around the top 5% for value and another 5% of bluffs. (Thats not a perfectly balanced range but these numbers are just for explanation.) So when you use a merged range your flatting range effectively becomes weaker as you are missing the top 10% of hands instead of the top 5%. Say your merged range is very simply 99+,AJs+ AQ+ and your polarized value range is QQ+, Aks, Ak. Your flatting range when you are 3 betting merged is now capped at 88, ATs and Aj while your flatting range for your polarized range still has JJ, AQs, AQ.
Also, if you are going to be pretty much raising or folding there is no need to include worse hands in your range. It makes no sense why you would 3 bet A3s but fold AJ. Why 3 bet AK and like A2s, A3s when you can use AK, ATs, AJs. Not only do AT, AJ have better blockers than A2, A3 but they have more equity against villains range. AJ has much better equity against TT than A3.
An example of some situations where you would want to have a merged range.
Good player opens in EP and you are in the SB. There are not many hands you can profitably call out of the small blind here. Absent of a big fish being the BB its reasonable to say you should just 3 bet or fold here so you would want to use a merged range.
There is a raise by a good player and another good player 3 bets. Generally you don't want to cold call too many 3 bets against good players as it puts your range a little face up. These are spots where I think you should either flat your whole range or cold 4 bet your whole range.
Being OOP against a good player. You generally don't want to flat too much OOP against good players so another spot where a merged range may be better.
Example of some situations where you want a polarized range.
A bad player raises and you are IP. IP against bad players you want to be playing, and flatting a large amount of hands.
You raise IP and someone in the Blinds 3 bets. IP you are going to want to flat some hands here and you want to use a polarized range to make sure you keep some strong hands in your flatting range.
There is a small raise, a lot callers and you are in the BB. Getting a good price in the BB you are going to call with a lot of hands here.
Plenty more example but those are some
Let me know what you think and if you think I said anything wrong. Definitely not an expert on this area.