Here you can see the contenders, the turkey egg on the left, with its gaudy speckled pattern and pale shell. It's significantly larger than the chicken egg, and has a more tapered top. More egg-shaped, you might say. Fancy that.
The chicken egg, on the right, is from a Columbian Blacktail, and is classified as large. You can just see the good old Lion mark on the bottom.
I ate the eggs side by side, if you can imagine that. Meaning that I cooked one after the other, then put them on the same plate (never allowing them to touch!). I ate them using the same fork, and for reasons of fairness, made sure to use the same mouth, tongue and tastebuds for each.
As for cooking method, both eggs were lightly scrambled using a four-tined steel fork, seasoned with both salt and pepper, and then cooked in unsalted butter (quite possibly more butter than was strictly necessary). I used my dedicated omlette pan, but I don't think it minded. No additional milk or butter was used in the scrambling process in order to preserve the distinct flavour of the different eggs.
The turkey egg had a larger yolk, as would be expected, and the cooked scramble was noticeably yellower than that from the hen egg. There were no nasty gloopy bits in the finished scramble, as there can be with goose eggs, and the texture was quite similar to the chicken egg.
I can report that the turkey egg was significantly tastier. There wasn't a particularly strong turkey flavour, but the flavour was definitely pleasant. Was it worth the price (£1.40 for a single egg, comparable with the price of half a dozen organic chicken eggs)? I think for novelty value it was. But I wouldn't want to spend that every day.
So there you have it: Turkey vs Chicken - Turkey wins!