 <p>Many of the Shiro developers use Spring for their applications, so Shiro works beautifully in Spring environments. The general feedback we've received thus far is that Shiro is also far easier to understand (for most people) than Spring Security.</p> <p>If you want full Session clustering support across any web container however, only Shiro will support this easily. Shiro's crypto is also very simple/easy to use.</p> <p>Choose which fits your mental model best - both will work great in Spring environments.</p>