i was in the exact same predicament two weeks ago, i have owned both before and had to decide between them again, and as much as i love the r10's looks i went with the hw100.
my heart said r10 but my head said hw100, this is the first time my head has ever won lol. the hw is clinically accurate and reliable, when the r10 works it is a good gun, but there are to many complaints about reliability for me and i prefer the simplicity of the hw mags