This is purely anecdotal but I've spoken to a lot of old Scottish racers from the 1950s and 60s during the course of my bike searching and almost all of them have expressed a preference for Stronglight cranks. Campagnolo and TA were both considered to break too easily. Those are guys who often had Campagnolo brakes and derailleurs so that seems a pretty unbiased, if unscientific, cross-section.
All of this talk has now got me wondering what to do with those nice shiny Campagnolo chainsets hanging on the wall of my lock-up. Mick Butler has also got me thinking about the round profile Chater Lea and hollow steel Duprat cranks I have as well. So much for the more easily broken cranks but is there anything out there from the '40s to the '70s that's pretty well guaranteed to withstand repeated pummelling beneath my not inconsiderable bulk?