Both are viable, but not in the same match-up
The First Sliver It may not be the only 5-color sliver, but its certainly the best
Bruse Tarl is a 3/3 with partner, and anytime it enters the battlefield or attacks, another fellow warrior can get lifelink and double strike (great for damage races)
If a battle has no defense counters, and it isn't the source of a triggered ability that has triggered but not yet left the stack, that battle is put into its owner's graveyard
Ever since it was created by the DCI (Duelists' Convocation International was the official sanctioning body for competitive play in Magic: The Gathering, aka bans and restrictions as well as tournament play) in January of 1994
The majority of cards remaining in your deck should revolve around that theme or goal youve identified