The Sprinco and Harrts are completely different. I have more than a dozen of the Sprinco units as well as a few Harrts. I use the Sprinco untis in both my P229 (.40) and P229 Sport (.357) and I am happy with the way they work. I started with the Harrts, but changed to the Spinco in the P229. The best thing about the Sprinco is that you can buy it and run it in your gun for 30 days, if you don't like it send it back for a full refund.
The Harrts unit does not reduce the slide velocity at all, as the Sprinco does, it reduces the upward flip of the muzzle. The work best on a larger bore pistol with a longer barrel, like a 1911 Govt or a SIG P220. Harrts do not work at all in compensated guns.
On a P229 I would recommend the Sprinco.