Help me to differentiate between Kenko TCs

Hello Friends

I came across the following two Kenko 1.4x Teleconverters:

1.   Kenko Teleplus DG Pro 300 1.4X Teleconverter ( http://www.smartshoppers.in/product/kenko-teleplus-mc4-af-14x-dgx-teleconverter-for-nikon/ )

2.   Kenko TelePlus MC4 AF 1.4X DGX Teleconverter ( http://www.smartshoppers.in/product/kenko-teleplus-dg-pro-300-14x-teleconverter-/ )

I intend to buy a 300 f4 AF-S Nikkor lens for my D90 with which I would like to use a 1.4x TC. After a lengthy discussion here and elsewhere, it seems that this combination will produce the sharpest IQ for least of the investment .

But I am not sure which of these two TCs is better optically . I found one German page which compared TCs and they declared the DGX is the best one. The DGX also costs about 40% less .

So please tell me:

1. Which of the above TCs will be better Optically with the lens I mentioned?

2. Are these Kenko TCs at par with the Nikon TC 14E II/14E? The Nikon's one will costs simply double of Kenko and also will not be useable with any Third Party Lenses, that much I am sure of.

Please help

Thank you

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