I am familiar with all of the guns you mentioned. I actually was on my way to get my cash when my local gun store had a VP9 that someone ordered and changed his mind. But after looking and handling the gun, I decided it was no P30. The P30 has a more "finished" feel to it, and although one is hammer and the other is striker fired, I like the size and feel of the P30 much more. It also fits together better, "not as many gaps".
The XDM is also one I have played around with getting in 9, I also carry and XDS sometimes. I love that gun. The problem with the XDM is the gun is blocky with that many rounds in it, and after holding it, I just didn't get that feeling that I get when a gun just works for me.
I picked up a Glock 30S, I already had a 30, so I sold it and it cost me 100 bucks to upgrade . If you are interested, the 30S is a heck of a gun, it's slim enough to carry, "the 30 was pushing it". And I bought a 13 round mag for reloads, and a front night sight, that I put on in 5 minutes, I do that on all my guns.
I am still looking for a 9mm and thinking of the FN line also. With these manufacturers coming out with a new model every week, it's a pain in the neck to keep up with when shopping.
Sometimes the old ways are still the best. Glocks always worked well for me, they may not be in vogue with all these new guns, but if it's not a 1911, it may be a glock 19.
One other one that I have found interesting but not shot, is the CZ, the P01 and the 2 Polymer pistols with 16 and 19 round capacity's. They are not expensive, and I like the idea of the rail running the full length of the pistol. I also may try a red dot on my next one, or on my 26 or 30. I have enough small pocket guns, I want a mid to full sized 9mm, that I don't have to worry about running out of ammo, if something happens and I have to grab it fast and go without time to get my extra mags. The VP9 was long also, not like the p30 3.85 length model, and not as nice to look at. I would take a Bitone XDM, and put night sights on it, sooner than the H&K, for about $549 on slickguns. I just think for me, it is a better gun. Plus they give you more for the money, till the end of the month you get 2 free mags and a mag older. You are really all set except for optics or sights. I don't like fiber optic sights, they are useless at night, I had to respond to a noise outside one night, grabbed the XDS, and couldn't see anything without turning on my light, which I don't like to do until I see or hear something move. The sights on the H&K is also a joke, after 15 minutes you have no night sight, so you are looking at another 100 plus for sights or more for a light or laser. Now we are up near 900 again with that gun. It isn't worth that to me. I can get a glock put on a night sight and it works for 700 or less.
The XDM is the same story, less expensive, more rounds and I like the feel and look of the gun better.The compact allows you to carry it with the 13 rounder, and daily HD use with the 19 rounder, same with the glock, you can use any mag from any 9mm..
The FNS I don't know enough about to make a comment, other than I would like to fire one, and they get good reviews from guys who have them, also the price is right, and you can put an optic on some models that are pre drilled should you ever decide to.