Well it really depends on which type of each you get, or end up getting. I've grown 3 types of chiles listed as "de arbol", one had 2-3" upright pointing chiles and was prolific until BLS got the best of it (it had small leaves and was very susceptible). Another type I grew last year, definitely had the tree shape and had very thin 3+" chiles that hung down, it was also quite picky in terms of moisture, and required dry conditions in order to flourish (which it did). After a heavy rain in which it wouldn't dry out after several days it would turn yellow and drop all but its newest leaves! Both types weren't as hot as I expected. The third type I am growing this year I grew from seeds harvested from dried "de arbol" chiles from a small Mexican store down the road, The dried chiles had some good heat to them and the plants have been flourishing in this heat, and don't seem as picky as the other two varieties I grew in the past, no pods yet though, as I started them very late.
"Japones" is another name that describes several possible cultivars. Basically, it seems like any Japanese, Chinese, or Thai chile may be grouped as a "japone". If it is 2-3" long, ripens to red, is quite hot, and grows upright in clusters, it may be called "chile japone". I guess the Yatsufusa chile may be the "true" "chiles japones" according to some seed sources like http://www.kitazawaseed.com/seed_238-104.html for example. I am growing the Yatsufusa this year and so far it seems quite resilient and prolific.