This pattern にしても is used when you want to say that your statement or opinion is the same no matter which of the given alternatives you consider. It often appears with pairs like ～か～ないか (whether or not) or with two contrasting options. For example, you might say that you will attend an event regardless of whether it rains or shines. The key nuance is that the speaker is brushing aside the differences between the options and focusing on a common outcome or judgment.

It is important to note that にしても has another common meaning, 'even if' or 'even though,' which is used in concessive contexts (e.g., 忙しいにしても、連絡くらいはできる). That usage is different from the one explained here. When you see にしても with a pair like AにしてもBにしても, it usually means 'whether A or B,' focusing on the irrelevance of the choice.

This pattern is fairly neutral and can be used in both speaking and writing, but it is more common in somewhat formal or logical discussions. In casual conversation, you might hear it, but it has a slightly reasoned tone.