Saving selections in a channel

[Ofnuts]

Warning, long answer...

The gut answer is no, it shouldn't matter... you should get identical selections. How to test:

• create a text layer
  
• Text to path, path to selection, save selection, rename channel to "From path"
  
• Alpha to selection, save selection, rename channel to "From alpha"
  
• Create white layer, get a selection from the "From path", bucket-fill
  
• Create white layer, get a selection from the "From alpha" channel, bucket-fill
  
• Create while layer, move under the text layer, merge down
  

You now have three seemingly identical layers. To compare them, make them visible by paris, put the top one in "difference" mode, which should give you a black image, then Layer>New from visible, look at the Histogram dialog. If you see just a thin vertical bar on value 0, then the "visible" contains ony pure black and both layer are identical. Otherwise there are differences (use "Curves" to make them more visible)

On my Linux, there are absolutely no differences between Alpha and Text, but there are noticeable (using the histogram) differences between the Path one and the other two. So, the alpha and the rendering of the text agree (which is expected since they are really the same thing). So for you the alpha could be what you call "more precise". However, on some platforms, if you have sub-pixel rendering enabled (almost always in current systems, in Windows it is called ClearType IIRC), the Cairo library used by Gimp will render the image using it, sometimes creating weird colors in the outline (this is very visible when you create white text over a black background). In which case, even if text and alpha agree, the real shape is the one from the path... But in that case, I create the text layer, get the path, delete the text layer, create a selection from the path, and bucket-fill it. This circumvents the outline colors, and then Text, Path, and Alpha all agree...