You could also say that Blue Snag is an error, plus it was only released in Sears and never on a card...though I know rumours still persist, so who knows!
However in general I see the VC/CLoth Jawa and Blue/red Snag as variations, major ones I know, but still variations. It's different to say the original R2 and the Sensorscope/pop up R2.
So for me a complete set includes 1 of every figure, released on a card/shown in the line up on the back, but not variations. It would not matter for me whether the Snag is blue, the Jawa in cloth, the Han with a big head, the Fett in Trilogo or the Ben with a basic saber. Just one would consitute a complete set.
Definitely not the Rebo band, Droid factory droids, Rancour etc.