If you would ask me about 330i vs. 330d, it couldn't be more obvious... Petrol all the way...
But in the entry class, the diesel should deliver more punch, especially in every day use... The small straight sixes lack a bit of torque, I think.
Both cars are no rocketship, so I might as well go for the cheap one, at least it is to run. (Based on my 20000km a year I drive. When you drive less, the petrol will be the cheaper one anyway...)
My point: Revving a petrol engine is only real fun if it revvs fast...
Buba