With email marketing, people are conditioned to delete most sales email unless it is something they have subscribed to. In PPC, people are seeking out your product or service since they clicked on your ad. From that perspective, PPC should be more effective as the person is ready to purchase.
I have to agree with the fact that email marketing has become a hard catch with everyone under paranoid firewalls and spam proof scanners. Fact of the matter is that PPC targets punters that are seeking that very information your looking to provide, thus making it very attractive to both parties. Might cost more to advertise PPC mode however in the right environment the benifit will be considered GREAT!
Both is necessary to see more products. I would recommend you to go for both as both are popular way of marketing..