You're raising an important point, by implication at least. The value proposition of a $300 Phottix is a bit different from that of a $167 Yongnuo. At $300 for a 580ex ii-like featureset I think I'd rather have a 580ex ii. At least the 580 can be repaired/refurbished, I assume.
There is a price threshold which makes the China-based flash solutions attractive compared to the latest Canon solution. For me, that threshold is a bit lower than $300. That said, the Phottex featureset (including their triggers) is attractive, to be sure, which means that your decision point may be more about features than price. If you value the Phottix featureset and the ability to update the flash in the future, then your decision is pretty much made -- especially if you are already invested in their triggers and have confidence in the promise of updates. The assumption here is that investing $300 today in an updatable Phottix flash will assure compatibiilty with future Canon cameras yet to be announced and which may introduce new things, i.e. a new ETTL version. that, or it assumes that bug fixes are addressed via firmware updates. I don't have any experience with Phottix, but something tells me that the inclusion of a USB port is more about bug fixes than adding new functionality to pace the market. There's no incentive, unless they charge money for firmware updates, for them to add new features to existing hardware. i would think they would rather sell more hardware . In the Phottix model, you pay more up front and expect hardware quality to be commensurate with a long term investment. When you update you get new life out of the same hardware. Kind of like putting new ink into a worn print head.
The Yongnuo model is different. Future proofing comes in the form of buying a new flash (the Yongnuos are just over half the cost of the Phottix). Yongnuo's quality model emphasizes initial quality and hardware repalcement under warranty, instead of firmware updates. You pay about half the cost up front, compared to Phottix (a third of the cost compared to Canon) leaving dollars on the table to invest in new hardware at a later date. When you update, you buy new hardware. kind of like replacing your ink cartridge instead of re-filling it.