Hi,
There really isn't a lot of difference nutritionally between whole grain wheat and whole grain spelt flours. Some people prefer to use spelt because it is an older grain variety and is less likely to have been grown by big agricultural concerns . If you look at the wiki articles for the two you can compare each nutrient.
Any grain that is finely ground will be relatively high on the glycaemic index so unfortunately whilst the whole grain flours have more nutrients than the white versions they will have similar effects on glucose levels.
(so for example a white spelt loaf had a GI of 65 an a wholegrain spelt loaf had a GI of 63).
Personally for pancakes I would use buckwheat, a pseudograin (relative of rhubarb!) As it's a flour it's still relatively high GI (about 54) but it works well and you don't need very large amounts to make pancakes (it's what they use in Brittany for savoury galettes).
You can use 'whole grain' flours for thickening but of course it means that white sauce will not be white.
I feel that the term whole grain is a bit of a misnomer should really mean what it says ie whole or cracked grains rather than milled grains.
http://www.culinate.com/articles/featur ... n_glossary
Using some of these in your cooking can require a bit of a shift rather than a substitution .