One advantage of using one workout on alternate days for a period of 1-2 weeks is that you get an idea of how THAT workout is working for you.
On the other hand, variety does help with motivation.
You could also have something between the two, and do one workout twice a week, and a different workout for your third (which I'd put between the repetitions of workout 1).
As far as 'results' are concerned, I don't think there's necessarily one 'best' choice, so go with what you want to do and what will keep you motivated.