If you want to kick off a lively discussion on a military based website then you have several choices. Aircraft carriers are one. Inter-service rivalries are another. Probably the grand daddy of them all though is to talk about gun calibres with respect to service rifles. It can get very heated at times.
The problem with such discussions is that it's very easy to make an unsupported assertion based on "common knowledge", but it takes a long time to systematically refute such arguments in the sort of detail that is required to satisfy even casual observers who have no dog in the fight. It's almost impossible to turn a "believer" against their chosen opinion, even with large quantities of what is practically irrefutable data.
One of the reasons I started this blog was so I could essentially write such responses in one place and then in future just drop a link to save myself much typing. Today I'm going to do just that for the infantry calibre debate, something that if you include underlying research I've been working on now for many years.