depends whos fitting it, you or a garage. a zetec E is more labour to fit which would remove the cost difference between both engines, but a zetec E will always have more long term tuning options as its a well known turbo engine route. Turboing puma zetec SE's is NOT done often and in terms of proper conversions (NOT gay low boost van aaken ones) has only been done 2 times and both were done by the same person.