Did they allow you to brake safely and avoid all accidents and collisions throughout their life cycle?
That's condition dependent, and somewhat in the eye of the beholder, I think.
Coming back down Mow Cop, they required more circumspection and forward planning than I was happy with, personally, given the degree to which some entrances onto that road obscure waiting vehicles. Riding with the Tektros, you'd need to keep speed down to be confident that the brakes would stop you within a safe distance (applying them more times throughout the descent). The Shimanos are effective enough that I feel happier at a higher speed. In the dry, on the flat, I'd suspect there's not a lot of difference (or what difference there is, isn't appreciable at the level I ride at).
However, I'm glad of the extra efficacy when descending, or in less than perfect conditions. So, to answer the question I *think* you're asking, the Tektros would be ok for someone either happy with a greater amount of risk than I am, or with a lower overall speed on descents and in inclement conditions.
If you want to test for yourself, I use Tiagra 9 speed levers (Triple on the front). The brake Giant spec'ed on my SCR2's model year was the "Tektro 521", apparently. I used the stock pads, then Koolstop Salmon, then Fibrax X-Treme in those brakes. I've only ever used the stock pads on the BR-650s.
The only collisions on that bike were due to a motorist entering a roundabout through my back wheel (the reason the DA22 wheelset weren't used with the new brakes, as the rear was rendered unrideable), and a slide on a patch of diesel. Sadly, neither were the sort of collision that required braking.