I already pointed out that performance issues are usually irrelevant in the question of whether to choose an OO design. However algorithms are also often irrelevant in whether to choose an OO design. Generally speaking you can write the same algorithms in any programming paradigm. OK, so some of them come more naturally in one paradigm than another, but the ones that come most naturally in an OO design are often not particularly efficient. Quite the contrary in fact.

For instance your memoizing object is the same algorithm as using an access function that memoizes its return. And using Dominus' Memoize module takes less setup work.

Now programming paradigms have a huge effect on overall program design. They affect how easy it is to swap out one algorithm for another (in obvious and not so obvious ways). I am not saying that all paradigms are created equal. (OTOH I think that which one is "best" depends on circumstances.) But in general programming people who think that raw performance is a good reason for them to choose one paradigm over another are generally wrong. And likewise decent paradigms are not distinguished by what algorithms they can express. (Now ease of expression is a different story...)