To start, let's define each term...
Normally, the idea is to alternate between the two phases until you are as muscular and as lean as they are looking to be. So before you decide which phase to enter first here are a list of things to consider: What is your goal right now? If its weight loss, how much fat do you have to lose?
If you have a lot of fat to lose, you do not want to start with a bulk phase.
Why? Well, when your fat percentage is already higher, your body is in storing mode. Therefore, when you keep adding more calories to your diet in attempt to gain muscle, there is a good chance your body will just store more fat.
So be honest with yourself here. If you think you are somewhat lean, then ok, you can go ahead and do a bulking phase. If you would not consider yourself somewhat lean, your best bet is to start with a cut.
Once you have put in the time and work to which ever phase you decide and your body starts to change we suggest trying to switch things up. Remember, your body will get used to the routine you set for it, so by switching it up you avoid plateaus and will continue to see results. You can continue to repeat the cut/bulk cycle and each time your body will be that much different. So take one long look in the mirror and decide which process your body looks like it needs to go through and give it all you've got.