The P30 is has a shorter OAL (by about .6"), OAL (by less than .1"), and lighter (by about an ounce and a half) than the M&P. It’s wider, though (about .2"), with a significantly shorter barrel (about .7"), and holds fewer rounds than the M&P (though it beats the P229). The P30’s triggers, IMHO, are marginal at best. The DA on HKs is still heavy and creepy feeling on traditional DA/SA guns; and the reset on the LEM will probably not thrill you compared to the P229’s. The P30’s grip is, possibly, the best “feeling” pistol grip I’ve ever held; and is widely adjustable to fit YOUR hand. The P30’s paddle magazine release is possibly the fastest and surest you’ll ever find, once you train yourself to use it properly - but it’s “unique,” so you’ll have to train yourself to get the best out of it. Lastly, the P30 is spendy, and, despite its hefty price tag, doesn’t come with NS. Spare magazines are sometimes hard to find, and also expensive…
The M&P is the largest of the three, but for open carry duty use, I don’t see that as an issue. It has the longest barrel, longest sight radius, and, arguably, the “best” trigger in that each pull is consistent and the reset is pretty darn short. On the down side, the trigger needs help out of the box, as the reset is very “soft” and hard to “catch” at speed - but those flaws are easily remedied with the Apex replacement parts. The M&P just never “felt” right in my hand, no matter what back strap I installed, but that’s almost certainly the fault of my hand, not the pistol as many users find it perfectly fine. S&W has THE BEST, bar none, warranty and CS in the business - if anything goes wrong with your M&P, they’ll make it right, at no cost to you, and FAST! The M&P is also SIGNIFICANTLY cheaper than either option, leaving money for training and accessories.
Lastly the Sigs. I really LOVE Sigs, especially SHOOTING a Sig like my P226R (pre-2005) in 9mm. They’re VERY accurate, due to their tight tolerances and precise machining. However, Sigs are pigs when it comes to size and especially WEIGHT efficiency. Seriously, either of the other options, LOADED will probably be the same weight as your P229 EMPTY. Ergonomics are very good, but the high bore axis over your hand likely makes the Sig “snappier” than either of the other options (though, if you haven’t shot them side by side, you probably don’t realize that yet). Nitron isn’t very robust, and the un-treated controls on my Sigs would rust while I watched them, practically. Sigs are prone to losing things like grip screws - I’ve lost count of the number of grip screws I’ve had to replace in the last decade of my guns and the guns of other team mates.
My agency used to be “Sig only” for authorized personal weapons. So, for about three years, I carried that P226R in the heat and humidity of coastal SE TX. Every night I had to wipe down all the controls and screws with lubricant to prevent rust. Off duty, I carried an authorized S&W airweight, because the Sig was simply too much of a boat anchor to slip into the waistband of my shorts. As soon as the authorized list opened up, I got Glocks, and never looked back.
If I were in your shoes, I would probably get the M&P, and an M&P compact for off duty, and two sets of the APEX “enhancement” trigger components. I really don’t think you’ll be disappointed. If the M&P doesn’t “feel” right in your hand, though, I’d go for the P30 - probably in the DA/SA, and think about sending it off to Gray Guns or some other competent smith to clean up the trigger a little.
Regards,
Kevin