They're really different classes of knives, in my mind. The para is much more pocket and user friendly, and the Manix has two real bests, ergonomics and tankocity.
The para is much lighter and thinner than the big manix (haven't handled the mini, but I assume that this is still true). Even though it's not as comfortable as the manix, it still feels great. Some people hate the tang sticking out of the para when closed, but it never bothered me. The mini manix looks like it has one similar too on the photos.
People are hard on the para's "high ride" clip, but honestly, the para is so long that I needed the high ride, or the clip wouldn't have gone all the way on in a lot of jeans. But yeah, you can definitely see some knife sticking out.
The compression lock is great too. VERY flickable (much more so than the manix) and can be flicked closed too, w/t practice. Very reliable and strong thus far.
To me, the para is everything you need and nothing you don't. It's just right tough enough for me...I don't need anything better built.
But I'm not everyone, so if you think you need more integrity than g10 and bilateral partial liners, then the manix is the clear choice. Also, like I said, the Manix is somewhat more comfortable.
If you decide to go with the para, I recommend you check it out yourself (or have NGK do it)...a lot of people disagree with me, but in my experience, there's a high incidence of minor flaws in the para. Here's what to check for:
off centered blade when closed
slight vertical play
poorly finished thumb ramp
too little resistance to keep it closed
Mine had all of these.