Sorry, I like Giant ... a friend recently bought one on my recomendation.. the welds did disapoint me but hey, what a value. I have a Rocky Mountain, it's stupid to compare the welds on a $2, 000 bike with a $500 bike. Anyway, I tried to dig up information on the Avalanche and Aggressor.
Aggressor: 7005 aluminium frame features GT Triple Triangle design with protapered downtube and replaceable rear derailleur hanger.
Avalanche: 7000 series aluminum, formed and tapered top tube, oversized bi-ovalized gusseted down tube, box chainstays, oversized constant radius seatstays
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Jeff