Are you the one having to decide which to install - if any? If not then you probably do not need to know but you could use Google and start reading articles. I noted that on the CA site one thing it said about Datacom was that it was faster to install - but it did not say what it was comparing against and the level of expertise used for the product(s) in question.
DB2 is much much better and choosen option over Datacom.
However, if you could search on internet with 'DB2 VS CA DATACOM Migrations' or 'DB2 VS CA DATACOM Comparision' then you would find many vendor's site noted down the information you are looking for and when you do so and then have any questions on your observations then please post it back so that experts here can share their views.