Silent Ones may have a higher Food to metal ratio, but their weekly resource value sucks. Silent Ones : 600k. Chimeras : 1.6m.
Resource value in this order : Chimeras (1.62m), PFs (1.31m), Reavers (1.21m), Dragons (1.17m), Wyverns (1.06m), Demons (1.03m), Griffins (1.02m), Golems/Barbarians (1.01m), Necro (0.95m), Nomad (0.93m), Warlock (0.88m), Great Lord (0.79m), Huntress (0.75m), Knight (0.73m), Paladin (0.66m), Pike/Silent One (0.60m), Archer (0.40m). This does not take into account training speed bonuses.
Offensive bests per oven are PFs, Reavers, Necros, Chimeras. Defensive bests per oven are Huntresses, Nomads, Golems, and Griffins.
Nomads over Barbs due to 10% higher food %. Golem over Demon due to 11% higher food %.
Absolute highest BG weekly banking is to build only Chimeras*, PFs, Reavers, and Demons/Golems. It does not matter whether you send to offensive or defensive, though if you want more Griffins than Dragons and Wyverns, you may need to utilize DJMOODY's comments above to achieve this.
Quest/Tournament rewards may mean that increased BG kills offset max banking and therefore mean use O and D only for their associated BGs.
*I'm not convinced that building chimeras for BGs is better than just building Dragons and Wyverns, as they're the whole purpose of BGs. I'd rather use the beastie oven to build whatever beastie I need at that time. Still, the extra rewards for BG tourneys and quests may make the potential for increased BG kills worth using Chimeras.
NOTE: I'd like to give credit to Xestos, of Legacy, for the creation of tables the above information was extracted from. I have verified most of the information and trust the whole.