Biggest difference in typeseting is that pdfTeX applies microtypography. Other than that, native TrueType and Type 1 fonts embedding and PDF features as hyperlinks, TOC and document information. PSTricks may fail, use PGF/TikZ instead.I think, modern LaTex uses pdftex. I did not know that pdftex use other algorithms than tex.
There is still raging debate among typographers is it Hz-program's microtypography the best thing since sliced bread or a heresy that should be burned at the stake.