The big advantage of replying to those with only postal access is that you will not have nearly as much competition, and you will have much more time to craft your letters to her. Sounds great, but the problem is that they don't usually have their own Email. The women usually have to use Email and translation services in their own country, which you are often asked to pay for. So what sounds like a great deal just isn't in the long run. Most agencies will provide you free access to their members but if you get a doubtful reply, or one asking for money, just head for the delete key.
Advantages Placing an ad is usually free.
Including a photo with your ad is free. It takes a couple of days for the photo to appear, but it's really essential if you want to get many replies. Browsing ads is free. You can't usually reply to them, but at least you can see if there are enough people in the database who appeal to you before you sign up. Email notification of new ads.