Welcome out of the ranks of lurkers; sorry your first post here was related to a preceived injustice you suffered.

From what I'm reading of your story the situation truly was in flux, so the fact that each agent had a different explanation was based on the fact that CO was changing things around in an effort to get you out of CLE and on to LAX as quickly as possible. As noted up-thread, planes that look the same are not necessarily the same model (73G, 738 and 739s all look a lot alike from the terminal, unless you're able to tell how long it is by eyeballing it in the dark), and even if they are, one plane may need to go to IAH instead of LAX that night or the next morning for maintenance or any number of other reasons. The planes (and the crews) cannot be shuffled so easily without a number of other things changing down the line.

You mention going to a CSR and asking about a reroute. You say that you would've made the LAX flight had you been rerouted "immediately." Is that immediately as in when you asked the CSR or when you arrived in CLE and noticed the delay? Are you sure that there were seats available on the CLE-IAH and IAH-LAX segments? There are several potential reasons you might not have been able to get on the IAH/LAX routing, even if you were standing at the gate. The fact that you had to suggest alternate routings (and there aren't that many) to the CSR is bad, but that's really the only thing I can think of where CO could have done a lot better, but again it is hard to know from where I'm sitting if you actually could have gotten on to those flights.

In the grand scheme of things a three hour delay isn't the best way to spend an evening, but there were both weather and mechanical issues and you and a hundred something others caught the delay. Sorry, but there isn't much else that is going to happen on that one.