With AVIA, there is a "point of reference" when using the filters, although you can always feel free to tweak the colours a bit by eye.
Each way would likely require about the same amount of time for the first calibration since the calibration is only one aspect of the overall time. It takes perhaps 1/2 hour to watch the AVIA and the Spyder DVDs so that you understand what to do and then you "do it".
The AVIA DVD also has additional test patterns that the Spyder doesn't have like sharpness, overscan, sound setup, etc.
The Spyder would be typically used in conjunction with or in addition to AVIA or DVE, not just instead.
I would certainly not spend $250+ for this device to simply do one or two TVs. I plan to use it in "future work" and if that doesn't pan out, I'll resell it.