I've had the P's for a few years now! All the pierces do is add certain extra characters (sometimes transformations depending on the pierce), extra items, backgrounds, and foods. Some pierces give you the ability to visit extra locations, but as mentioned it really does depend on the pierce! You may already know about this though. XD
To get to my point - I've never gotten my hands on
any of the pierces, nor do I have a way to download extra content through iRDA. With or without them, the P's is still a really
really fun version to run, and there is a bunch of things to do/characters to raise/locations to unlock and so on and so forth. My P's is beat-up and scratched to death (oops) so if you do pick one up, don't do what I did, haha!!! It's a version worth taking care of, to sum it up. And I do like the shell design - it's very pretty! I always end up fidgeting with the pierce port though. XD This version is known for losing its shell colour/yellowing over time easily (though this applies to most of the colour versions), so be careful when storing it and taking it around!
Basically, if you're willing to take the risk price-wise, the P's is a very fun 'gotchi to own. There's a few differences between it and the ON (such as the obvious language barrier, unless you've got a way to patch it - I am forever envious of those who can
), but those differences are what make it unique and fun. This has gone on for pretty long now, so if you're still unsure I'd recommend some further research and seeing what you like about it. I hope this helped you out!