Here is a (uncompressed) photo showing the two ereaders side by side and with a A4 paper for having an idea of the size (with and without the "crop" zoom):
I guess that if you want to read only scientific articles (which are usually on A4 size), a 13.3" reader will be better. I don't know the Sony, but Onyx one is nice (and it can support many many formats, which is a big advantage).