Which one is more time-consuming? Multiple TH1 or Single TH2

(Sorry in advance, I’m not sure this is the right place to ask this question.)

When we want to make histograms for two variables, we can simply use one 2d histogram.
Or we can use multiple 1d histograms (such that the single 2d histogram equals the merged 1d histograms.)

I wonder which way is more time-consuming to deal with. (to define, fill, save, and fetch the histogram.)

And in similar way, which one is better?
multiple th2 or single th3?


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I would say the performances regarding filling should be the same, but the usage is not the same. Regarding a TH2 as a collection of TH1 is not right. As soon as you will try to do operations on them for instance “fitting” you will have problems.

Thanks for answering!