eTTL is a pretty amazing technology, and it allows for types of flash photography that is impossible with manual flash. It also adds convenience and can produce acceptable results quicker, which for certain types of professional photographers affects the bottom line, profit. So I’m not being dismissive of it at all, I just don’t have much of a use for it when doing off-camera lighting – for my work. Furthermore I think there are plenty of people who use it off-camera more out of lack of ability with manual, or just for convenience. Which is fine, I just prefer the fine tune and control of manual over the convenience of eTTL.
Third party options provided a very economical way into lighting for me, and allowed a lot of flexibility in starting small and growing my lighting setup. That may not be as important to you, or you may put more weight than I put in having uniform setup of matching lights and modifiers for consistency. It may also not be worth your time to research dozens of different options; I find the process entertaining. Such things might steer you towards the Canon setup.
I think one thing we can all agree on, is that lighting is one of the most complex elements of photography. So with complexity will come more variation on personal preference. I’m just glad to have options.
