I don't have the appropriate crank bolt socket, so I use a standard Ace socket set. The socket is tall enough that when torqueing up the bolt with it's shallow head, it's easy for it to slip off. I really have to work to keep the socket square to the head. It's much easier to have allen heads. Plus then I can just carry my multitool and have everything I need to tighten up the bolt in the field. Getting out 5 or 6 miles towards the trailhead on your 52" singlespeed mtb and feeling the left side crank start to flop all over is a good way to learn that lesson. "Hmm... do I gingerly pedal all the way home and hope I don't trash the crank or do I walk the whole way? Decisions, decisions."