Typically, most of these services are uniform—i.e. include the same tools and features (send a script, they record it in a tone you approve, they send it as a file, you supply any feedback, etc.); however, there are some services that go above and beyond. For example, VoiceOverPro, is a single voice professional who records 30 second voicemail messages based on users’ scripts. This is standard; however, users also have options like adding music, recording up to 60 seconds (or 150 words), rush, 2-day turnaround, and even same day delivery.
Even in today's fast-paced world, customers don't like being greeted with an automated message. According to the New York Times, callers of a certain age are put off entirely if they are answered by a voicemail instead of a real person.

You can’t always get to the phone when clients, partners, investors, or colleagues call you. When this happens, a professional voicemail greeting helps you make a positive impression and tells them what to do next. There are a variety of ways to convey your message. If you’re not sure what type of message to record for your own voicemail box, here’s a definitive guide to get you started.
When your business is closed for vacation or holidays, it’s imperative that you set appropriate expectations for a callback and to provide an alternative coverage option, if available. The following greeting accomplishes this succinctly.