One question would be why they were sent to different institutions.  I vaguely remember reading Clifton had some other issues, but I can't find it at the moment.  

Even so, look at what each did with his time in prison. I have not seen anything to indicate that Clifton set his mind to education & positive pursuits. Maybe he did, but one would think if there was something sympathetic to say, this article would have included it. One of the articles noted that Lima said he cut ties with Clifton because he still talked about doing bad things Lima didn't want a part of.  

As for injustice, I think injustice occurred when an overzealous prosecutor chose a method that resulted in 98 year sentences. Both men suffered from that injustice.  One can debate whether it was fair that one man got out very early through not only luck but also his exhibition of character change. I've already said Clifton's sentence needs review.  I think injustice would be either one serving the full, unjust sentence