I'm not sure I would mention brisket and tri-tip in the same phrase except that both are beef cuts of meat. One is the toughest cut requiring hours of slow cooking to soften the connective tissues to get an edible piece of meat (brisket) from the front of the animal. The other is from the rear area, and is tender enough to grill without any special prep, and when cooked and cut properly it is super tender and very tasty.
As a Calif. dude I cook and eat a lot of tri-tip each year. Traditionally it is simply seasoned with salt, pepper and garlic powder, grilled. Served with pinquito beans, salsa, green salad and grilled garlic bread. If not serving with beans then I like baby red potatoes seasoned with BBQ seasoning and grilled.
Tri-tip cooks slower than other steak because the cut is thicker. Tri-tip is a cut from the bottom sirloin primal cut. It is a small triangular muscle, usually 1.5 to 2.5 lbs.
If not cut on the bias, then the slice with be tough and chewy, when cut properly it is super tender and yum good.