I added a comparison of the major logging/tracing frameworks for .NET to the CodePlex site for Essential.Diagnostics, to demonstrate how System.Diagnostics stacks up against log4net, NLog and the Enterprise Library.
I also added a performance comparison (the source code is in the CodePlex project if you want to verify the results).
Look at the results for yourself, but I think System.Diagnostics does okay — and the extensions in Essential.Diagnostics (plus others such as Ukadc.Diagnostics and UdpPocketTrace) fill out the gaps compared to log4net and NLog. Similarly on the performance side, all have very little overhead (NLog is a winner on overhead, but does relatively worse on actually writing the messages to a log file).
What about the Enterprise Library Logging Application Block? Well, I just don’t think it does well compared to the others. Sure it was a lot better than .NET 1.0 System.Diagnostics, but a lot of that was added in .NET 2.0 System.Diagnostics (such as multiple sources). In some cases it is worse than what is currently available in the standard framework — e.g. no delayed formatting. This shows up in the performance figures which indicate several magnitudes greater overhead than any of the other frameworks!
I’m obviously biased, but I really think that the best solution is to stick with the standard, out-of-the-box, System.Diagnostics, extended where necessary to fill any gaps (Essential.Diagnostics, etc, for additional listeners, filters & formatting).
P.S. Also check out my guidance on Logging Levels.