Relative merits of TCs vs DX Cameras with zooms.

[NRandall]

The title should explain my question to some degree, as I try to decide whether or not to buy a TC-14E of some description for my 300mm f/4 AFS lens.
I did mean Telephoto though - not zoom - my bad :o
Below is a crop showing around 20% of an original from a handheld photo at Kangaroo Island last week.
Taken with a D610, I could have alternatively used the D7000 and cropped less albeit with less resolution.
Given the ratings for the TC-14s suggest a 5% reduction in sharpness, how does this number for the D610 shot, relate qualitatively to the decrease in detail I would have had from the D7000 on its own?
Has anyone seen or done the math / numbers / comparisons for this kind of question?
http://farm6.staticflickr.com/5514/11082307325_4f768dc561_b.jpg (http://www.flickr.com/photos/104578175@N05/11082307325/)
265468 (http://www.flickr.com/photos/104578175@N05/11082307325/) by randaldinga (http://www.flickr.com/people/104578175@N05/), on Flickr

[arthurking83]

HERE's (http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=651&Camera=614&Sample=0&FLI=0&API=2&LensComp=651&CameraComp=614&SampleComp=0&FLIComp=1&APIComp=3) a pictorial comparison of the difference between a bare 300/4 v's a 300/4+1.4xTC.

hover your mouse over and away from the image to flick between the two images.

It doesn't specify which TC is used(that I can see) but you'd assume a Nikon TC14E would be the most likely candidate.

[NRandall]

HERE's (http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=651&Camera=614&Sample=0&FLI=0&API=2&LensComp=651&CameraComp=614&SampleComp=0&FLIComp=1&APIComp=3) a pictorial comparison of the difference between a bare 300/4 v's a 300/4+1.4xTC.

hover your mouse over and away from the image to flick between the two images.

It doesn't specify which TC is used(that I can see) but you'd assume a Nikon TC14E would be the most likely candidate.

Thank you for directing me to this site.
My first impression is that CA is fairly pronounced with the TC, and that the loss of sharpness seems more significant than the theoretical 5% some describe for the TC-14. Possibly, it could be the loss of sharpness combined with the CA. It would be interesting to see how things look with CA corrected so I might go ahead and buy a TC and find out more.