Richard is one of the best digiscopers there is. It is more down to him and his skill and ability making use of the equipment rather the 'what' equipment he uses. Either that or he's sold his soul..........! o
I feel qualified to answer your question as I have a 77 Apo and HAD a 62 Apo. I got far better results in UK with the bigger scope, no doubt. I use 20x on the zoom and disagree with Scampo in that 62mm is better for digiscoping - maybe for bigger subjects and where you are close, but for small passerines 20x ( on a 77 ) is better, even when "close".
I now use a DSLR but have to say that some of my best pics are digiscoped esp. Crossbills which is my thing. The DSLR is easier to use though....see the bird, 'shoot' the bird ! My Gallery is no longer here but will be on my website soon.
Go for the Apo 77, it is a cracking scope, amazing optical quality. Oh, and I believe mine has gone up in value as have my Swaro Bins - could sell them now and make money ( ish ), certainly not lose it !
Hope this helps,
Linz