I have only deployed 4.2.130 and have no issues. 5.0 is not recommended and 5.1 is too new. 4.1.173 just came out and states that it fixes issues with 1250 ap's, but if you don't have 1250's then I would say 4.2.130 since you are already on the 4.2 code. I have deployed 4.1.185 on WiSM's and standalone wlcs when I do not have 1250's in the environment. But again, you are on 4.2 so just stay on 4.2.
126.96.36.199 has the AssureWave logo, which means that Cisco have simulated a whole bunch of real life scenario configurations in their labs and they verify that there are no issues. I am using 188.8.131.52 and do not have any issues.