There is a third option. Your naive and believe what people tell you without thinking it through. Mesa boogie is in the business to to sell amps. Believe it or not, they want to sell new amps, because that money goes to them rather than someone selling an old amp and having the money go to someone else. So they tell you there is no difference between two models. If you were to call up and ask if the lead channels on the Three channel dual rectifiers sound the same as the two channels, they'll say "Yep sure nuff". This isn't true. There are very major changes between those amps. If you were to call pepsi and ask if cane sugar pepsi tastes the same as high fructose corn syrup pepsi, they'll say "Yep sure nuff". In both cases they just want to sell you new products and will lie to you to do it.
So, to summarize, the changes between those models of triaxis's matters, and do affect the sound. Just like changing the dual rectifiers from ldr's to relays changed their sound, and using corn syrup for pepsi changes pepsi's flavor.