I can only speak to my experience with older Martin Logans. So you can take the following comments as you see fit...

I used to own the Sequel and we sold lots of those along with the Monolith and CLS at the store.

The Vista looks a like like a modern interpretation of the Sequel, which was also a hybrid. As gonk said, they can be pretty placement sensitive. I recall the smaller the stat' panel, the smaller the sweet spot was. In addtion, compared to conventional box speakers I have owned, they just are not as dynamic. Apart from the woofer enclosure, you just can't move as much air around with that sheet of mylar as you can with conventional drivers. If they're going into a system where you'll listen to movies at high levels, that may be a consideration. Bottom line is, don't push 'em too hard. Again, that is based on older ML's -- perhaps things have improved in that area.

Lastly, MLs were quite sensitive to electronics. For example, CLS's were a favorite choice to have in the evaluation rooms of high-end electronics manufacturers as they were stunningly revealing. In your recent listening session where you said they sounded like crap, perhaps it was because of poorly matched equipment???

When I purchased my one and only tube preamp, it was based on having the Sequels. At the time, I powered them with an Aragon 4004. Both electronics were on the warm side to counter-balance the Sequels' tendency to sound thin and bright. Today, that combo on my current speakers would be way too caramel sweet sounding.

Their strenghts? Very open and transparent when you've got them dialed in. And like most electrostatics, transient response is excellent -- they're really, really fast. The cool looks factor is also a bonus when showing the speakers to neighbors, friends, hot chicks, etc.

One final thing, if you do settle on them, be sure to plug them into a good power conditioner with adequate surge protection. And keep kiddies with sharp objects away from the panels.

Not familar with the DefTechs, so I'll shut my mouth on that one.

Be sure to let us know what you end up with!