That's impossible to guess, because the answers are weighted based on how hard they are and how early in the test they are. So if you leave blank any questions in the first 10-15, that would hurt your score more so than in the last 10-15.
At any rate, it's definitely better to guess, but try not to guess randomly unless you're totally out of time. I would recommend trying PR's strategies for making educated guesses (via process of elimination), and failing that, pick a letter to use if you have to totally guess - i.e., choose C for each remaining question, rather than trying to decide on each one which letter to pick.
As this is a CAT, you cannot leave questions blank throughout the test - only stop early and leave a certain remainder (say, the last five questions) blank.
To address the question, I do not know whether it is better to guess or leave blank.