The only difference is the token's stats : For Mirrodin! spawns a 2/2 red creature token with the rebel creature type, and living weapon gives you a 0/0 black creature token with the Phyrexian and germ creature types
Most starter decks are well-rounded enough that they can hold their own against casual constructed decks
GODEEPER: The Blue/Yellow combination is a consistent theme across competitive OPTCG, and the full breakdown of how dual-color leaders build their card pools is in the One Piece TCG Deck Building Guide
Playing some games with a few extra points of life was very good in some matchups and some formats even had life gain matters themes which these played into perfectly
The An-Zerrins have served me well, ever since I first killed them. Baron Sengir Illustrated by Dennis Detwiller Part of the Reserved List Standard Not Legal Alchemy Not Legal Pioneer Not Legal Historic Not Legal Modern Not Legal Brawl Not Legal Legacy Legal Comp
In a deck with cheaper interaction and other spells, well, not so much