I wanted to understand the point of having 50fps on the 28mbps and not 25fps?
How do you guys record in your productions?
*If i wanted to have better sound in my recordings should i record on AVCHD?

I'm recording for broadcast in the future, i want to get me a ninja 2 or a star in order to get the 4:2:2 color space. Which one of these suited for better results in 25fps?

Wanted to better understand the 25pf. What is that for?

The only difference between AVCHD and MP4 is that MP4 has Dolby Digital compressed audio (192Kps) versus the LPCM track on AVCHD. Frankly, unless you're doing a lot of audio volume tweaking, you'd be hard pressed to tell the difference, and I usually rely on MP4 for all of my needs save for when I'm shooting something in which captured audio on site is a key part of the video (i.e. not just b-roll).

PF25 is a 50i video stream with 2:2 pulldown added to embed the 25p signal within it.