The lolis are almost the same character and even if the character background isn't exactly the same, they surely are very similar in that aspect as well. Despite both being a comedy, the plot in both series isn't as shallow as one might think.
Even when putting all the similarities aside, it's a must watch show for people who love lolis. Uzamaid got the perverted lolicon maid who is very direct when it comes to her superior taste in women (both in the script and in the animation) and Astarotte is more ecchi themed with lots of loli fanservice. The art/animation in both series is a huge turn on and very rare for anime that cater to intellectuals like myself.