I found myself with time on my hands yesterday near Oakland Chinatown, so I decided to do a head-to-head comparison of the egg custard tarts from Napolean Super Bakery and Ruby King (I would have done pork buns, too, but Napolean was sold out).
The version from Ruby King was slightly smaller than the one from Napolean, but also slightly less expensive (55 cents vs. 70 cents, IIRC). The Ruby King crust was flakier but also a little softer, with a mouthfeel that hinted at lard instead of butter. The fillings were quite different: Napolean's was sweeter and had a strong vanilla note, while Ruby King's had a more pure custard flavor.
Verdict: while both are good, I personally preferred the Ruby King version, which seemed more traditional, to the Napolean version, which seemed more influenced by European style pastries.