I have a SL66 and can confirm that it is a PITA used handheld. OTOH at least in Germany it is comparatively cheap. The Habla and SL66 do weight nearly the same if you compare a whole system consisting of the usual lens set of 50, 80, 150 and 250mm.
If you prefer leaf shutter I suggest having a look at the 600x system from Rollei. They can be had for a song.