With all that is said about price and value, TS you need to go to the store and test them. I tested both the Alu and CF versions of the alta pro series. With center column in vari angle, I gave the legs a light tap, and watched in amazement as the center columns vibrate like crazy (both CF and alu versions). And the legs flex like nobody's business. Even the low end siruis did much better. The CF version alta pro costs almost $500. I got my explorer for mid $500s (before the price hike and at a limited time special discount). Tested in TK with uncle phillip. Even he told me to avoid the alta pros after he saw my test, shaking his head in the process.
But in the end, it is your money and your decision. Find real value. And not perceived value through reasoning without testing the products in real life.
Personally, even if the alta pros are priced same as manfrotto xprob, I will still take the xprob over the vanguards.