Judit -
I'm a Sound Lab owner and dealer, and I used to own Maggie 3.6's. I listened for a while to 3.6's and M-1's in the same system.
The Maggies are a little more efficient. The Sound Labs are considerably more articulate, especially at low volume levels. I kept wanting to turn up the Maggies to hear the nuance and harmonic richness that was so easy to hear on the Sound Labs. And, as you might expect, the big Sound Labs go quite a bit deeper - but this is a matter of sheer panel size, not electrostatic technology vs ribbon/planar magnetic technology.
The Sound Labs also do something that is extremely rare - they project the same tonal balance throughout the listening room. Very few few speakers do this, although it's a characteristic of live music.
As Blueswan correctly points out, a well set-up pair of Maggie 3.6's share many of the same attributes with the Sound Labs. If there wasn't already a Maggie dealer in my town (New Orleans), I'd be a Maggie dealer as well. The 3.6 is extremely competitive in its price range.
Duke