In 9mm sig I currently own a P320 and a P226 x5 allround among other sig calibers. I used to own a P226 combat as well and fired everything from the elites to the basic nitron. I also have a P226 LDC on pre-order. Out of them all I love my x5 but they are in a class of their own as well as price.
The regular nitron P226 is a solid pistol and heavier than the P320. It's has a metal frame which gives it its weight and helps manage perceived recoil despite its higher bore axis. There are also a number of different variants so it should be easier to find the style that suits you best. My personal favourites are the elite models outside of the mastershop, x5, x6 family of 226s. The elites usually come with a short reset trigger (SRT) and a match barrel. The Tacops is also very nice and comes with a SRT but I can't remember if they still have a match barrel. I personally didn't find any discernible accuracy differences while shooting the mk25 or combat over the any of the other non-match pistols although they do come with a more resilient milspecs to combat weathering and treatment. There are also two grip variations, regular grips and the e2 grip (enhanced ergonomics). The e2 grips are designed to reduced the grip circumference and look like a wrap around grip whereas the regular grips basically sandwich the frame. In gerenal there are a lot of choices between styles, finishes, grips, parts and accessories.
The P320 on the other hand is a reworked P250 without a hammer and striker mechanism. Its has a polymer pistol grip vice the P226s metal one. In order to fit your hand you have to order a complete lower frame. (S,M,L). Since the serial number is on the fire control unit and not on the frame itself its a straight forward swap. There may not be as many parts for the P320 since it is new but luckily most of the P250 accessories such as magazines, holsters and frames also fit the P320. Out of the box I was extremely impressed with its accuracy. First shot cold barrel hit dead bull at 15m so I've been partial to it ever since. The trigger is smooth and crisp unlike the loose sloppy trigger I have in my 45 P227 nitron. Its doesn't have the play I found in stock factory triggers but not as short as the factory SRTs. I truly enjoy shooting this pistol. As for striker fire preference, I shoot this over my Glock G34 now and is much farther ahead than my M&P 9 Pro with an apex trigger. Again this is subjective to personal preferences. but for 9mm it rivals range time with my Shadow SP-01 after the x5 for tactical/sport shooting. Since I bought the small grip for my wife I've all but lost the pistol. She also prefers it over her PPQ Navy. Much like the P250, Sig officially confirmed they have caliber x-change kits for the P320 in 9mm, 40 and 357 sig with a price around the $300 USD mark. Hopefully they will add 45 to the list like they eventually did with the P250. What impressed me is that you can complete a full conversion in less than a minute. So if other calibers are something you would like in the future then the P320 is for you.
Anyway, over all the P320 would be my preference against any of the non-match barrel 226s. That being said I would probably pick an elite over the P320 for accuracy. But for the price point the P320 is a great pistol over the elites especially if you want to shoot other calibers. I guess if cost is the truly limiting factor the P2022 is a"thirfty" version of a 226.
Again this is a subjective question but I am sure the forum will help steer you to your own conclusions.
A harder question will be whether I like the P320 over the HK VP9 (or Canadian FN Sport version) or the Arsenal Firearms Strike One. Only time will tell.