Whether you are or aren't yet a fan of classical and Irish flute, you will very likely enjoy the following: https://youtu.be/b1SPfXOGXEQ
It's just under an hour of virtuoso classical flautist James Galway and virtuoso traditional flautist Matt Molloy trading tunes and some light commentary about their music during a special evening programme (\end{UK-spelling}). Beautiful music, lovely contrast. Great banter from Galway. And an added bonus at the end: a Molloy-Galway pennywhistle duet!
Some major differences in technique:
1) Molloy makes frequent use of a wide variety of ornamentations expected of a high-level traditional Irish flute player: cuts, rolls, crans, and so on. These also usually substitute for tonguing, even for two consecutive notes on the same pitch. In classical flute these ornaments simply do not exist (the closest thing to a cut is a grace note, but they actually serve completely different purposes). Cutting instead of tonguing is unthinkable.
2) Galway uses vibrato extensively and it comes from his throat (that's what Galway himself maintains, anyway; others say it's chiefly the diaphragm). When Molloy does do vibrato, you can see his finger quivering over an open hole to produce the sound. This is another area in which traditional Irish playing favors finger techniques over lip/tongue/throat ones.
3) Galway has a large dynamic range. The Boehm system flute, i.e. the modern keyed flute, allows for a much wider and subtler dynamic palette. Molloy, along with many traditional players, is not nearly as interested in dynamics.
The repertoire is its own discussion.