I've used both Mimic and the demo version of textPuppet. Here are my impressions.

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textPuppet's strengths:

Built-in speech synthesis. Currently has support for U.S. English, U.K. English, French, Canadian French, German, Italian, Portuguese, and Spanish. Has a few additional animation options that Mimic lacks. Lower base price than Mimic.

textPuppet's weaknesses:

If you have prerecorded speech files, there is no easy way to lipsync them with textPuppet. Only for Windows PCs.

Mimic's strengths:

Works with any form of prerecorded speech. Available for both Windows and Macintosh.

Mimic's weaknesses:

No direct support for foreign languages. Fewer animation options. Higher base price than textPuppet.

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Having said all that, I still prefer Mimic, because it's more versatile. textPuppet only uses synthesized speech, but Mimic can use both natural speech and synthesized speech (freeware speech synthesizers are available on the 'Net).

As far as lipsync accuracy and animation quality are concerned, each program has its own advantages and faults. I'll let you judge for yourself.

Below are a couple of animations created in Poser with both textPuppet and Mimic. I ran textPuppet first to create a synthesized voice file, then fed that same voice into Mimic. I've put both animations side-by-side for easier comparison.

Take the Pepsi Challenge (video in MPEG format, 683KB)