VoiceAttack uses the Microsoft speech recognition engine, so dictation accuracy would be pretty much identical between it and the built-in Windows speech recognition application.
Training your speech recognition profile is essential for dictation, so make sure you run the training multiple times (three, at the very least).
For Microsoft Office applications, apparently they have
a cloud-based dictation service, provided you're an Office 365 subscriber.
I can't personally speak to the accuracy of this service, but for dictation, cloud-based services do tend to do better than offline systems (with the disadvantage that anything you say does get sent to the provider of said service).
For offline dictation, Dragon Naturally Speaking is pretty much the industry standard, as far as I'm aware.