Bloody hell twinset, it's Friday night, we should both be getting merrily pissed not discussing Aristotle!
OK, you draw a thing that looks a bit like an aerial view of 5 cowboys peeing in a bucket (central circle, 5 circles connected to it). Everyone (or 'A's of pairs) writes Aristotle in the 'bucket' - images of God on the 'cowboys'.
'B's meanwhile do the same for Christian images of God.
You can obviously pair up abler/less able students & give more able the trickier task, which I'm guessing in this instance would be Aristotle.
Then you have a diagram which is two big circles, with (say) 4 little circles in between them - lines connecting - those are for similarities, & another 4 little circles which are just connected to 'Aristotle', & 4 which are just connected to 'Christian'. It looks like 2 spiders holding hands 4 times iyswim...
Each pair agree which beliefs are common to both (holding hands) & which are one only (free hands).
They then number the similarities in order of priority (first half of essay) & then the differences (second half of essay).
You can use the diagrams on an interactive whiteboard - draw one, scan it in, scribble on it yourself or get students to. You can then print blank versions off to save initial faffing about drawing circles etc.
Once they get their heads round it, you can move away from it 'having' to be a set number of points - students can have however many 'cowboys' or legs' they judge the task needs.