Very interesting how, in the 'real world', this focal length determinant is not mired in absolutes. Different lenses create different effects. That attitude, more than anything else, is refreshing, as it segues into the creative element. Some things are worse today but this is an example of thinking that is truly better. Benjiboy's suggestion that one use a 70-150 (assuming for the ability to determine 'on the fly') is potent. Also, agnosticnikon's assertion that even a 500mm (!) portrait was not only acceptable but WANTED by the client (over the others) was interesting.
The feedback here is great and telling, not only from the standpoint of technique, but also from the standpoint of human nature. More opinions are welcome (if not already mentioned). - David Lyga