Developing a Medical Protocol Index - Should I use one master XML Document or a database of XML files?

I am developing an index of Medical Protocols to be used on a website and in mobile apps. The client has requested that they be stored in XML so that they can change the output format using CSS depending on the media that they publish to (e.g. Website, Print).

A simple example of the hierarchy of the data is as follows:

<Medical Protocols>
    <Protocol Category>
        <Individual Protocol>
            <Title></Title>
            <Preamble></Preamble>
            <Steps></Steps> {Number of items with this tag will vary}
            <Epilogue></Epilogue>
            <Notes></Notes>
            <StandingOrders></StandingOrders>
            <PhysiciansOrders></PhysiciansOrders>
        </Individual Protocol>
    </Protocol Category>
</Medical Protocol>

Any advice or thoughts on which direction I should go in would be greatly appreciated. If you have any questions or need any more information, please let me know and I will answer to the best of my ability.