XAML VS C# - Performance differences

In my current project I experienced performance issues when navigating to a page with a ListView. The ListView has generally 30 entries (or more).
The navigation to the page took 1.5 seconds or longer (UI freezes). After changing the ItemTemplate from a GridLayout to an AbsoluteLayout the performance was a little bit improved. However, I was surprised when I noticed that the performance could be further improved when implementing the ItemTemplates not with XAML but with C# code (Performance gain of approximately 0.5s).

I didn't found anything about this issue on the Xamarin website. In my oppinion, such a difference should be better documented.
I find it convenient to use XAML but I rather choose the implementation with C# code than XAML when I see this differences.