Brian at Brianstropicals.com uses both java and riccia and talks about what he likes/dislikes about them. He has pics of both in his tanks, which will give you an idea as to the growth habit of each of them:
brianstropicals.com/building
riccia stays very short which is great for foreground and waterfall areas. Java moss can grow rather tall for a moss and has a jungly appearence. Brian suggusts keeping bigger dart frogs in java moss tanks so that the moss gets trampled down in place. He specializes in darts btw- and his basement has over 50 dart tanks!

(but he also breeds zebra plecos and other fish- check out his site, he sells the young and even has unrelated breeders set up for other hobby people like himself.)
*I am not affiliated with Brianstropicals

I just found the site not too long ago and was elated with his basement setup! lol