Kenko KNT-20 2X vs. Tiffen Megaplus 2X

Which one of these two teleconverters is the best?

I know the question might sound silly but i can't tell from the pictures on lensmateonline.com which one has better picture quality and the least amount of vignetting.

Please tell me based on your experience with any of these teleconverters which one you consider to be the best.

I am considering buying one of these two and I really need opinions and reviews before doing this.

I have a G6.

Check out this page: Kazutoku's famous G1&G2 report ... it's for the G2/G3, but I think that much of what was posted there still holds true for the G6, as the optics should be rather similar.

I had the Kenko KNT-20 on my G2, and I liked it a lot. Availability was also pretty good, as I was able to order it through a normal Tokina dealer (Kenko being a subdivision of Tokina).

The only thing to bear in mind is that - although the thread diameter is 52 mm - the rear pupil of the KNT-20 actually has a diameter of just around 30 mm. It did not vignette on full zoom (3x) on my G2, but vignetting started when I zoomed in a bit (e.g. at 2.5x zoom). But I assume that's the same with the other converters, as well. I know for sure for the Olympus TCON-17.

Also, check out olympusauctions (new products in dented packages sold by Olympus with full warranty], they sometimes have great deals on Olympus teleconverters (also among the best available).

Best regards,
Andy