Jessup is considered to be the standard grip tape, and it is the grip we offer for free with all decks. MOB is known for their coarser grip, which gives excellent traction, but also wears down your shoes faster. MOB M-80, Grizzly and Shake Junt grip tapes fall somewhere in the middle, offering good overall traction without the heavy abrasion. There are other extra course grip options for downhill skateboarding (Vicious, Blood Orange, etc.). That stuff locks your foot in place but it is so coarse it would quickly destroy your shoes if you tried flip tricks with it.
Without good grip tape, skaters have a tough time staying on top of their board. The main complaints about poor grip tape tend to be that it was never very grippy or lost its grip really quickly. Once again, we recommend trusting in name brands with years of experience supporting skateboarders. Unfortunately, if you are buying a pre-made complete skateboard, you probably won't have access to the brand name of the grip.