An Over Bustle is attached up on
the outside of the skirt.
This is a French Bustle where the train is attached up underneath the skirt.
When choosing a bustle for your wedding gown consider the following. If your train is really full or has a lot of detail near the bottom of the train generally the Over Buslte will show off the train better.
If your train is plain or there is detail running the length of the train generally the French Bustle looks good.
There are always exceptions to this and when I see your dress on I can better tell and show you what would look the best. Recently with a lot of the lace or net gowns which have multiple layers with varying degree of fulness both types of bustles are used.