Usage of 'future perfect' versus 'future simple'

Both are grammatical. Both are perfectly normal (though the form with have is probably less common).

They have different meanings: not in the sense that they describe different sets of circumstances, but that they look at them in different ways.

I will finish my money by the end of the week is not focussing on a time, or if it is, it is focussing on a time before the end of the week: it is looking into the future.

I will have finished my money by the end of the week is placing the viewpoint at the end of the week, when all the money has gone. It is looking into (what will then be) the past from a point in the future.

Both ways of speaking are grammatical, but they different in their use.

I will finish all my money by the end of the week.

Use of will often indicates a promise or decision. In this case, it could be an affirmation. Without further context, it's difficult to see what the use was.

I will have finished all my money by the end of the week.

Here the suggested meaning is evaluative, a prediction. Appears regretful. Again without context this may not be the case, but it's subtly different.

Caveat: I recognise that there are many more uses for the two including predictive qualities for future simple, but you really need context or more examples rather than simply comparing two examples of the form.

Source: Own expertise - Development editor for digital learning content.