Vikram,
In trying to answer your questions, I'm afraid that I have been a little long winded.
I have fired the P225 (9mm), P6 (9mm), P220 (.45 ACP), P228 (9mm), P226 (.40).
I own a P225 and I gave my P6 to my daughter. They are essentially identical.
The German police force specified three pistols when they went away from the PPK. Some of the lessons they learned, especially after the 1972 Munich Olympics hostage crisis, was that they needed a larger caliber and more firepower. In answer to their specifications, they were offered three pistols; the Walther P5, the Sig Sauer P6 and the H&K P7. They purchased all three. However, the pistol purchased in the largest number was the Sig Sauer P6. All three pistols were chambered in 9mm Luger. This SIG Sauer pistol was later offered on the civilian market with a lighter hammer spring, a standard hammer and Van Stavenhagen (dot-bar) sights (with three dot Siglite night sights as an option). This model was called the P225 and has since been discontinued because the P239 offers the same features in a more compact pistol.
When they retired these pistols, something like 30,000 of them, they were purchased by importers and resold in the US. Many of these guns had holster wear but like most police pistols, they were barely used inside. I purchased one of the P6's. My daughter liked my P6 so I gave it to her when she got her permit to carry. Shortly after that I was lucky enough to find a P225 at a local gun shop. The pistol is basically a P220 with a shortened slide and a grip. This gives one a relatively compact 9mm pistol with 8+1 capacity. It is a double action/single action pistol which means that the first shot has a long stiffer pull (8 lbs to 12 lbs) and subsequent shots after the hammer is cocked by the slide are only about 3 lbs to 5 lbs. The gun has no manual safety. The long heavy double action pull is your safety. There is also a metal tab that locks firing pin movement. When the trigger is pulled all the way back, a lever pushes the firing pin safety out of the way allowing it to move forward when struck by the hammer. There is decocker that allows you to drop the hammer safely on a loaded chamber.
Generally the SIG pistols have been DA/SA handguns. The classic SIG Sauer pistol has an anodized Aluminum alloy frame and a folded (pressed) carbon steel slide. The slide was pressed into shape from a single piece of sheet metal with the nose piece being welded on. This welding is so exceptional that it is impossible to see from the outside. The steel slide rides on the alloy rails of the frame. These handguns were made in Germany and imported here. These had matching serial numbers on the frame, slide and barrel. The slides were not blued but finished with a proprietary black finish called "Nitron". No folded slide guns were made in the US. Sig's motto at the time was "To Hell and Back Reliability". This was used in many of their ads.
Today the slides are machined out of a solid piece of stainless steel (like the video) and they are made both here in the US and in Germany. Many SIG aficionados swear that the folded slide models balance better with the stainless slides making the guns top heavy. I really haven't noticed that.
My impressions: keep in mind that these are my impressions
P6/P225
All the SIG's that I have fired have been accurate, very reliable and extremely durable. If I have a negative, I would say that the finish on the Nitron finished pistols tends to wear rather quickly. As an Indian, I have a much smaller hand than most Americans and the P225 fits me like it was made for me. I am able to access all the controls without shifting my grip. Using this gun in competition, I was able to recover from each shot very quickly and make accurate, closely spaced double taps. Many people, when they hold a P225 for the first time will say ; "Ahh"! It just fits. As one poster on SigForum said; "P225-like pulling Excalibur from the stone". These are both folded slide guns and still in demand, even though they have been eclipsed by the P239 and other guns. P225 are not that easy to find as most people who have them, won't sell them. P6's are a little easier to find but the price has doubled since they were first offered on the surplus market.
P226
Full size gun, great to shoot, fast target reacquisition after the first shot. Relatively low recoil but I wouldn't want to carry the weight around all day.
P220
Smooth and low recoil for a .45.
P228
The double stack magazine cause the grip to be wider than the P225. Controls are a little harder to reach without shifting the grip. Other wise it is very similar in size to the P225. Not as ergonomic for me.
All of these were very accurate and had no failures when I was using them. Keep in mind that these were all service pistols but the accuracy for me was better than your average service pistol.
The current SIG Sauer pistol line up consists of:
P210- 9mm - This was SIG's first pistol (before the collaboration with JP Sauer and Sohn). This was the Swiss army's standard pistol for many years. They are renowned for their accuracy and very much in demand by shooters. Their value seems to preclude their being used in competition anymore. Sig has brought back this pistol now as the P210 Legend.
P220 - .45 ACP. - Sig Sauer's original big bore pistol.
P226 - 9mm, .40 S&W and 357 SIG. This was a very popular pistol for SIG. When the fabled Seal Team 6 under Dick Marcinko had problems with the issue Beretta's, they evaluated a bunch of pistols but chose the SIG P226 as one of their standard weapons. A pistol similar to the one used by the Seals is offered to civilians as the "P226 Navy". I have read reports on SIGForum that one issue P226, used for training, went over a quarter of a million rounds before it suffered a major failure!
P229 - 9mm, .40 S&W, .357 SIG. This was the successor of the P228 with a railed frame and a stainless slide.
P232 - .380 ACP - This is a compact blow-back pistol
P238 - .380 ACP - This is SIG's Colt Mustang lookalike in .380 ACP
P239 - 9mm, .40 S&W, .357 SIG. This is a compact sized pistol (See Cottage Cheese's avatar)
P250 - 9mm, .40 S&W, .357 SIG, .45 ACP. Polymer framed pistol offered with many different frame and slide combinations to make a pistol that fits your needs. Double Action Only
P290 - 9mm. Ultra-compact polymer framed pistol. Double Action only.
SP2022 - Polymer full sized DA/SA pistol renowned for its smooth trigger.
1911- 1911 clones
P522 - .22 LR. This offers the look and feel of SIG's 556 rifle with a shorter barrel and no butt-stock.
P556 - 5.56 X 45 NATO. This is a short barreled 556 rifle without the butt-stock.
Note: Each model is offered in many different configurations; like the "combat", the "elite", a two tone version, etc. The P226 X5 that ckkalyan fired is in almost a different category by itself. It is almost a custom pistol renowned for its smooth single action trigger, its accuracy and it reliability in competition.
2011 SIG Catalog. Warning! large - 38 Megs