The Prius is a new car to the market + its a hybrid,so the'll be high maintanence cost,but in the mean time it gives you better km per gallon compared to a Allion and also you drive enviromentaly friendly .The Allion is a known car,with ample of spares availabel cheeply...If ure consideration is the petrol consumption,it is the prius,but when taking other factors on average,the Allion is way ahead.......My choice would be the Allion.Good luck.....Btw what is the model of the Allion you are reffering to