IMO, since the cape buffalo has never been domesticated to any significant degree, it is therefore probably wilder and more dangerous than water buffalos.

The Asian swamp buffalo in Australia ia a wild(or feral if you will) and agile animal, capable of soaking up much lead, but still capable of being rounded up and domesticated. IMO, he is as much fun to hunt as the cape buffalo, and just as tough, and maybe tougher, physically.

The feral River buffalo (milk buffalo) of Europe and South America can be somewhat less muscular and less agile and less wild than the others, but can still be quite wild and dangerous. It is not generally as physically impressive as the others. The chromosome count is different between the River and the Swamp types. There are many different breeds of milk buffalo.

There are plenty of domestic cattle that are wild as march-hares, and some that will permanently turn out one's lights. I believe that the scrub-bulls of Australia, Texas, and South America have similiar reputations in this regard.

FWIW Chromosome Counts (2n)
Domestic cattle and American bison= 60
Cape buffalo= 52
Swamp buffalo=48
River buffalo=50
Gaur=58