It depends on what you are trying to achieve and how you are doing it. A well-written XSLT macro will probably work better than a poorly-written .NET macro and vice versa. XSLT is fast and elegant when manipulating XML to display data, but quickly becomes cumbersome when trying to interact with user interaction, for example. The rule of thumb that I use is that if you just show the data, use XSLT, but if you need some kind of user interaction, use .NET.