It has more features than Poser 7.

For me, the main reason for buying Poser Pro was gamma correction. I was gradually learning about this when I had Poser 7, and it dawned on me that to get proper gamma correction using Poser 7 I would have to convert every single shader that I used. Poser Pro has gamma correction built in. You still need to learn about it, but it's much easier with Poser Pro.

The second main reason was the Background rendering and the Queue Manager.

With Background rendering I can start a render within Poser (say to check certain aspects of a scene, or a partial scene) and then continue to work on other parts of the scene while it is rendering.

The Queue Manager is a batch render manager. You can send a render to the Queue Manager, and it saves a 'snapshot' of your complete scene and then renders it outside of Poser. This means you can close Poser down and do other stuff, like go to bed maybe, or open up another scene file. The Queue Manager can also manage a small 'render farm' of several computers rendering one scene.

Poser Pro also has the option to use a 64-bit Firefly render engine, if your computer and OS are 64 bit. It's quicker than the 32-bit Firefly engine.

I went for the Poser Pro Base version. It's cheaper and I do not need the advanced Poserfusion interfaces and import/export facilities that the full version gives.

"If I were a shadow, I know I wouldn't like to be half of what I should be."
Mr Otsuka, the old black tomcat in Kafka on the Shore (Haruki Murakami)