I agree with Tammy. If they are offering low resolution pictures on a disc, that is typically only meant for proofing. The quality is okay enough that you'll be able to tell which pictures you want... and then you will be forced to order them from your photographer.
With a high resolution disc and all personal rights to the pictures, you can print them, make photo books from them... or 10 years down the line you can do something with them. I really feel that the high resolution disc is the way to go. However, many photographers will charge for the disc since print prices are where they can make a lot of money, so you'll probably end up paying more for their services. But, when you add up the cost of all the prints... it gets REALLY expensive. Just something to think about! Let me know if you have any more questions and I'll do my best to answer them!