The longer your cable run the greater the cross sectional area of copper you want plus the heavier gauge cable is never going to be an issue with a higher power AV Amp.
We have used both cables with the various 'Eggs' and unless the budget is being really squeezed would tend to use the 2x2.5mm.
I did mean would the performance difference be noticeable.
As long as they are similar then I will choose based on size and colour once I have finally decided how they will be mounted.