Tamron MC4 1,4X and/or Kenko Pz-AF 1,5

[pikipoki]

Hello

I know I read allready a few things about these converters here but I just can't find the threads anymore so I'm starting a new one.
Maybe it will help a few more people not just me.

So my first question would be are these the two that work with SDM?
I am getting a 50-135 and a few mm added on the long end would be very helpful sometimes...but not all the time. So I thought a converter would be a much better choice (smaller, lighter, cheaper...) then a new lens...and there is no other lens with a constant f4...except for the 60-250 but that one is big, heavy and expensive and I really don't need the extra mm that often.

Does the kenko take more than 1 stop since it is 1.5?

How is the quality of these 2? Sharpness, coolurs, CA, does the AF get any slower...?

Since the Kenko sells for 90$ on e-bay and the Tamron for 199$ one should think it is clear which one is better, but I would realy like to hear opinions from people who have used one or even both.

Thanks

Matej