Does choosing the right marketing voice matter when communicating to prospective clients? I would suggest that it does. People feel comfortable when they read marketing material that is written in their own voice. Therefore it makes sense to work out who your audience is and then work out how they communicate to each other.
This doesn't mean to say that people conciously prefer reading things written in their own voice, it just means that they don't realise that they're doing it. So if you write in a different voice then they'll definitely notice it and you'll be thought of as an outsider.
Lets take an example. If you're trying to communicate to millenials, would you speak to them in the Queen's english? Probably not. As you're putting together marketing content, be aware of the words and phrases that your target audience are using. Do they swear? Are there any insider words or phrases that they use?
Speaking in the correct marketing voice identifies you as “one of them”, which builds trust and makes you accepted. You avoid being discovered as an outsider.
For example, if you're talking to a European audience about football then don't use the word 'soccer' or you'll be treated as an outsider. If you're trying to market to Yorkshire folk, don't use 'Eeh Bah Gum' in your marketing material as no-one says that anymore!
Also bear in mind that different styles can be tested and the responses measured to see which style produces the best result. This is much easier in the digital age. Also, the marketing voice used may want to be changed depending on the product or service that is being sold.
Choosing the right marketing voice is a time proven strategy that works. Its part of understanding and knowing your audience and you'll get greater take up of your product or service offering if you use this method.