Ken,
They are completely different beasts.
Briskets are best cooked at low temp (210-250 degrees) in a Smoker and taken out when the meat reaches a high temp (195+ degrees). I generally cook them with a basic rub. Sometimes, I'll let it soak in a basic beef marinade. Either way, when making BBQ beef sandwiches, you can't beat a slow and low smoked brisket served in a good french roll with a few dashes of warm BBQ sauce.
On the other hand, Tri-Tip, while not a sear and serve cut, is cooked much quicker than a brisket. IMHO, Tri-Tip is best cooked indirect at higher temps (300-350 degrees) and then given a final sear over extreme heat. Unlike brisket, which is cooked well past "well done" (160 degrees), Tri-Tip is best pulled at medium-rare to medium(135-145 degrees). It is a cut of meat that you can be very inventive with in terms of marinade. I'll make them from Sonoran style to Santa Maria style to Southeast Asian style to Japanese style to Napa Style to Greek Style to Southwestern to Middle Eastern. My personal favs are Sonoran tri-tip tacos (served in home-made corn tortillas topped with a great smoked salsa, a slice of avocado and some creme fraische), a Southwest Tri-Tip Cheesesteak(served on a grilled french roll smothered with roasted NM chiles, Jack cheese and a corn black bean relish) and finally, my favorite, Teriyaki Tri-Tip Sandwich (on a crusty french roll with honey wasabi mayo and topped with Asian coleslaw).
As for serving, the key to both cuts is to slice across the muscle grain. IMHO, I think that Tri-Tip is best cut very thin (1/16") and Brisket cut a bit thicker (1/4").
Anyway, I like both brisket and tri-tip... They just have different ways in which they shine.
