Heterochromatin v Euchromatin. Which is more abundant?
Percentage of euchromatin varies between cell types and organisms. It has been shown that upto 88% of the human genome is transcribed; a phenomenon called pervasive transcription [1]. Highly specialized cells may have a lower percentage of transcribed regions and in females one entire X-chromosome is silenced (some regions in the silenced-X do show transcriptional activity).

Euchromatic regions not only constitute the geneic regions but also regulatory intergenic regions such as enhancers, locus control regions (LCR), silencers etc. It has been found that ~97% of these elements fall in the DNAse hypersensitve (DHS) region of the chromatin [2].

DNAse hypersensitivity is directly proportional to the chromatin state such that open/accessible regions are more prone to DNAse-I digestion. You may call these regions as euchromatin.

Though the total DHS density is not reported in the paper [2] or supplementary data, the ENCODE project that the paper concerns, will have all the detailed information. You can can find these datasets here, from which you can calculate DHS density distribution for different cell types. However, most of these cells are actually cell lines and not from primary tissues.