undecided

We have been on several land, small cruise, river cruise Tauck tours in the past. We are looking into Jan 2017 Cruising Down under West bound NZ/AU cruise which is 19 days vrs Grand Australia New Zealand which is 20 days. Cost aside, which btw, the cruise seems to be substatially higher but apparently covers more, I was wondering which would be a better options. I know alot has to do with personal preferences but being that this is the only continent that we have not visited, I would welcome input from Tauck Travellers, and please note that I do not say recomendations, as that is very delicate. Thank you in advance