My take is the base C7 is still one helluva machine. After that, you are merely adding to the factory available amount of awesome you want to apply. If you are a cruiser, the 1LT base is ample. Gonna track the car? You have to go with the Z51 in my books. Iffin' ya just gotta have the most power and capability available, then double the base price and get the Z06 with all its toys (Z07). If interior is your bag, that's where the 3LT and 3LZ come into play.
Take a hint from C7Jake. If you plan on doing mods of any significance, go with the base and throw the savings at the mods.
I have the Z51 2LT A8. I wanted the added capability of the Z51 even though I probably will not track the car. No plans to mod the car other than maybe some better breathing like a higher CFM cold air intake. I couldn't justify the added cost for the interior upgrades of 3LT though. The Z06 is just outta my price league plain and simple. I already have added austerity meals to my food budget to afford the Z51. Can you say KD and weenies?