Never used email marketing but I have used sales letters/flyers sent via the mail, these worked very well in the case of flyers (retail spaces), letters tended to take a much longer response. 18 months in one case which cost us just a £1 and brought in £2500 in recurring fees P/A. So ive always found it use full.
The choice between the two should be which one has the price offering you like, plus the interface you can get on with. There are templates you can use to save developing a new format, and you can leave the e-mail delivery to the business that knows what it's doing.
There are many alternatives, but the two you mentioned are quite acceptable. Run a trial with one of them and see how you get on.