Canon 250D is equivalent of +4 (250mm) and 5T/6T is around +3 which means that 250D will provide a higher magnification. Optically wise, they say that both produce sharp image as it is high-quality achromatic types. And these glasses retain the AF function of the lens.
Filter size for 250D is available on 52mm/58mm, 500D is 72mm, Nikon 3T/4T is 52mm and Nikon 5T/6T is 62mm. Which means that if your lens filter size doesn’t match, then you may need a step up or step down ring (cost about 15$?).
Price for Canon 250D is about 145$
They say Nikon 5T/6T is half the price, so, around 70$
Bare in mind that additional lens degrade image quality somehow… so, consider using extension tube, although AF won’t work, but you’ll hardly need it for macro work. Or, if budget allows, go and get Macro Lens!!!