To me, Hens and Chicks is a name, a common proper name, so I would list it all with capital letters, just looks better that way, just my humble opinion.
When you look at your semp database
http://garden.org/plants/brows... I see the majority as Hen and Chicks (although the first 2 are just Hen and Chick, an only child?
Anyways, the genus listing would look cleaner if it was all the common names were consistently listed the same. I love the clean look of the Rose, Iris and Daylily databases,
http://garden.org/plants/brows... with just one common name.
Thinking of the future search function, what would the every day common gardener not knowing the proper genus name search for? Houseleek, Hen and Chicks? If they are all the same, the search will bring up the entire list and you can still have the additional common names added too.