Just got back from the range. The results from these Compacts were predictable CZ excellence, especially with the upgrades on the guns. Top notch performance, and I am thrilled with both purchases, as usual.
I didn't perceive any difference in recoil between the CZ75C and the SP Compact. I did notice that with the 17 lb spring, I could see the front sight of the SP Compact more quickly for slightly faster follow-up shots, probably due to the slight extra weight bias from the SP Compact's forward-heavy railed frame. With the 20 lb recoil spring, that difference went away mostly. I found that both guns functioned flawlessly with a wide range of standard and +p ammo, with just the stock 17 lb flat recoil spring on stainless guide rods. Hotter +p ammo did not batter the guns, and a heavier recoil spring was not necessary. I had 100% feed, function, and consistent, strong, flawless ejection about 5 to 7 feet away, depending on the load.
Both guns' sights are set up for center hold, rather than 6 o'clock hold or frame hold, which only took a moment to get used to, and the sights were perfectly centered. Both guns will consistently fire a six-shot 1" hole at 15 yards, and a nice 1.25" pattern at 20 yards, slow-fire, when I do my part. These are extremely accurate CZ's, equal to a full sized CZ, and no upgraded barrel bushing is necessary.
I could also consistently dump 10 rounds in about 5 seconds into a 1.5" to 2" ragged pattern at 15 yards, with little effort, using just the stock sights. Recoil is minimal with factory fmj loads, and very manageable with +p hollow points. Both guns performed every bit as well as my full-sized CZ's, and are much faster to clear a holster with.
Both Compacts preferred lighter, faster rounds, and also preferred hotter loads. They performed equally well with economical Fiocchi 115gr fmj, Winchester White Box 115r fmj, and CCI Blazer brass 115gr fmj, shooting them like some finely tuned full-sized target guns will. And both guns' accuracy load for self-defense purposes was the Speer Gold Dot 115 gr hollow point, with Fiocchi's 115 grain extrema Hornady XTP load a close second.
Neither gun particularly liked S&B 124 grain fmj, American Eagle 124 gr fmj, or Fiocchi 147 gr hollow points. It seems the rifling and twist rate of the shorter CZ barrels want a lighter, faster round in order to spin up and stabilize things, if I had to speculate. Groups weren't bad, they just weren't as consistent or tight as with the several 115 grain loads I tried.
Below is typical of what the SP Compact produced at 15 yards, dumping 10 rounds of 115 grain fmj at a pretty good pace using the stock 17lb recoil spring. The range I was at wouldn't tolerate super-fast double and triples so I will test that at the Sportsman's club next week.

The CZ75C produces similar groups, and this is typical of what it produced at 20 yards at a medium pace. What a joy to shoot!

To put things into perspective here, after nearly 400 rounds downrange, not a single misfeed, double feed, misfire, fte, light strike, etc. The magazines work perfectly. And the average groups these pistols delivered inside 20 yards all morning, with just about all ammo tried, will fit inside their trigger guard!!! I honestly don't shoot much differently with my costly, tricked-out custom Shadows, at these close self-defense distances. And I doubt I'll be shooting my compacts much out past 25 yards LOL!
I can't recommend these Compacts highly enough, if you are comfortable carrying a steel-frame pistol. I also highly recommend the 13 lb hammer spring, an extended firing pin, and if you have the means, and the skill to install it, a race hammer and disconnect. The double action is totally use-able now, and the single action is perfect to keep you from pulling fliers, without being too light. Reset is short, consistent, predictable and crisp. There is no need to buy a costly custom compact. With a little motivation, a willingness to dabble in some DIY, and a little extra cash for the excellent aftermarket parts now available, you can produce your own Custom Compact for about half the price of what the custom builders are charging.
The only thing I need to do now is install and test the TS safety on the SP Compact, because I found the ultra-slim safety that came on it was nearly useless today, for my purposes.
And then I think I'll sell my blocky, clumsy, sloppy, cheap-feeling, annoying 2015 Glock 26, which took me weeks to sort out, and required several different pricey aftermarket and upgrade parts, just so it would stop flinging burning-hot brass directly into my face at 90mph for three out of every 10 rounds. In short, I hate it, and will be glad to see it go. This has been true of most (several) Glocks I've purchased after 2011, right up through 2016, and I am through with buying any more new Glocks, because they are no longer machined with the correct slide tolerances that they once were, no longer have quality internals, have terrible resale value, and have been just loaded with unpleasant issues. This is the total opposite of my older Gen2 and early Gen3 Glocks, all of which I still have and treasure like my CZ's. I'm no Glock hater, I love all guns, but it is long overdue time to call it like it is nowadays....How would you rather spend YOUR $550 -$650? On a gun that is now deliberately made cheaper than what you pay for it, and is a high risk of performing poorly right out of the box, or on a gun that is far better made than the money you spent on it, and performs beyond your expectations? For the same price....
CZ's, unlike Glock and Sig, just keep getting better and better, offering more and more great new models as well. I'm gonna go clean these puppies, and celebrate the huge win they represent.
And many thanks to Scarlett, whose diligent posts tipped me off to the existence of the SP Compact!!!!