Old vs New - 500mm vs 70-200 Sigmas

[Fangman]

Chaffinch full frame with the 500mm f7.2. iso 800 1/125 f7.2 needed for the 500mm with contrast boosted in Lightroom

Starling 70-200 f2.8 about 40% crop. iso 100 used 1/100 at F3.2

I really miss the ease of framing with the zoom on the Sigma 2.8 and autofocus seems pedantic on the fixed 500mm. Results seem easier with the shorter focus lens even though I crop to get the framing needed - near focus at 3.5 meters on the older lens is a bind as my feeders are nearer than this. On the other hand, Ely Cathedral a couple of miles away seems almost in my back garden with what amounts to an 800mm equivalent on 35mm