Ive also got a set of Shamal Ultras, and a set of Bora Ultras. Rode my Shamals for the first time this morning since February, and i must say I was really amazed at how good they are. Ive been racing with the Boras for a few months now, and I am pretty used to them, but riding the Shamals agian i think they are not far behind at all. With a decent tyre (ive got GP4000s) on the Shamal, those wheels are very fast. The Boras go to a higher pressure, and you can feel the difference in the ride (11 Bar as apposed to 8) but is not that significant. Its not like the one wheel is way faster than the other, you just feel the road vibrations a bit more through the Bora. On the climbs the wheels are pretty much equal, as the weight difference is probably less than 100g. Where i do prefer the Shamals is on the decents, and in the wet, as the braking on the carbon surface is just no where near that of the Shamal. I feel a lot more confident on the Shamals in the rain! In the sprints i prefer the Bora, firstly the sound that they make when you stand is really cool, and the fact that they have the 50mm deep rim which is very stiff. No visable rub on my brake blocks, even when im flat out. And the aero advantage is great, the wheel just feels faster than the Shamal when you hammer it! One thing i noticed immidiatly when i got the Boras was how easy it was to jump across a few meters to a break, as the wheel feels like it accelerates instantly to your pedal input. As Spidy said, in the bunch you wont feel any difference between the two. With both you will easily be able to cruise at 40-45km/h, and be able to follow the attacks. The Shamal is a nice wheel, much nicer than my old Ksyrium SL's, and almost as good as the Bora. But honestly i dont think the advantages of the Bora justifies the price difference between the two. Both wheels have their pros and cons, but if i had to choose i would rather ride a wheel where i dont have to stress about punctures all the time, (the inconvinience and the cost of replacing a tubby) and also get the superior braking performance from the alu rim. If i had a choice and could only choose one, i would go for the Shamal, and then spend the spare R10k on other stuff to lighten my bike. Maybe some Zero Gravity calipers, or some really light bars, stem, saddle etc. And if i was buying now, i would also wait, as im quite interested to see how the tubeless Corimas perform in the long term. I think those may be the way forward! Hope that helps!