Thank you for your question. Every time JustTrace takes a memory snapshot it uses ICorProfilerInfo::ForceGC
method. As far as I know there is no difference in the implementation of ICorProfilerInfo::ForceGC() and System.GC.Collect() methods.
I would like to point you to this blog post
which I find useful. The results I get with JustTrace, Visual Studio and GC.Collect() are quite similar.
All the best,
the Telerik team