My discussion note under http://www.entmp.org/HGrk/papers/ gives a more
technical overview.
If people have comments or criticisms of either documents, please let me
know.
The pronunciation you describe as learning originally is the
pronunciation of Modern Greek. The other pronunciation that you've come
across is a compromise between Classical Greek, Hellenistic Greek and
English that is convenient for English-speakers. No one ever actually
spoke Greek like that, though.
James K. Tauber <jtauber@entmp.org>
Associate Director, Electronic New Testament Manuscripts Project