i've tried both. i used to write shader programs in assembler instructions but i tried fxPascal and implemented it in my last engine. It generally worked pretty neatly but it had a few shortcommings when working with multiple rendertargets and arrays and such. but generally i like it.

Glsl.. well i've used it a bit and frankly i don't see why i should use it. I havent' been able to find any reasons.

if it doesn't come with a pdf with all commands and syntax included then it is in Seth, an IDE for fxPascal