Is 10.10.5 more stable than 10.10.0?
Stability is hard to prognosticate - even if you have all the crash data that is sent to Apple or by harvesting the logs of thousands of Mac computers. Projecting the stability of a system in general to one person't specific list of modifications generally makes these comparisons poor and subjective.

What I can say is that 10.10.5 is more secure than 10.10.0 and again more secure than 10.9.5 but neither is as secure as 10.11 (which I find to be very stable - even running the beta builds, it was as stable for me as 10.10.x)

Part of me is divided, if you haven't jumped to 10.10 yet, my feeling is don't bother. You get these few features - http://www.imore.com/os-x-el-capitan-review - continuity, Photos and no big changes under the hood as 10.9 already has compressed memory. 

I would say wait for 10.11.1 and then upgrade since most of the consumer crashers and allowances needed for third party apps will be out for the .1


Office for 10.11 is fine
Virtual Box for 10.11 is fine
homebrew and shell is better on 10.11 than 10.10/10.9 in my opinion
Metal on 10.11 will make pixelmator and other apps far more responsive if your hardware qualifies for that acceleration.
You'll want to ditch iPhoto if you go to 10.11 (probably) and iTunes might work a little better - hard to say on these two, though


From http://www.apple.com/osx/how-to-upgrade/


  Metal is supported by the following Mac models:     
  
  
  MacBook (Early 2015)  
  MacBook Pro (Mid 2012 or newer)  
  MacBook Air (Mid 2012 or newer)  
  Mac mini (Late 2012 or newer)  
  iMac (Late 2012 or newer)  
  Mac Pro (Late 2013 and newer)