We very occasionally use rings on very young calves - yes, just like ringing a lamb. As long as you check you have two testicles fully ensnared, just as you would with a lamb, it's fine - but does only work very early on (or the calf and its testicles are too large) and needs a strong person to restrain the calf.
Our normal practice is the burdizzo at 2-3 months old. The calf's early growth is unchecked, and frankly we rarely if ever see any problems clamping them this way.
However, it requires quite a bit of strength and a great deal of technique. When BH's wrist was injured we had a number of people help us with this task - and have had a few vet bills subsequently, correcting incomplete castrations.
If for any reason we don't get to the lads with the burdizzos by 3 months old, then it's a vet job - slit, pull - just as s_b had done. The lads certainly feel a bit sorry for themselves for a day or two after that job.
