The NAA Guardian will be heavier than the other three, and in your pocket, that will make a difference. The other three seem to all be proven guns at this point, even though the Taurus is relativly the new kid on the block. Check the importance of the features of all three and how it feels in your hand. The accuracy reported on the Taurus sounds superior to the P3AT and the LCP just from what I have read. There is another gun to consider called the Diamond Back which looks like a mini glock. My favorite lgs has all 5 most of the time which makes side by side comparison easier. I have the P3AT and have had it for over two years, so I haven't put much effort into comparison other than features and ergonomics and what I've read. So far, nothing I've read makes me want anything else enough to take a loss on the P3AT as it serves it's purpose well. The LCP is basicly a P3AT clone with a slide lock and is better looking and feels a little better to hold.
Here is a good write up on the Diamond Back .380 with pictures, specs and comparisons in size to the P3AT, TCP and LCP