I have the jtech 3.8, I love it, and their Jay's customer service
I looked a long time at the 7w, but there's just so little good documentation, and no other reviews. If I'm going to spend the $$ for that, for a few bucks more I can get the 40w, and it has a huge fan-base.
Only downside to the 40, is size, I'm spoiled by the XC and 1000x1000, so i would probably use it until I exceeded the capacity, then rip out the guts, put them on a larger markerslide increase the size. I see that as the least cost alternative, and with an XC I can fabricate much of what id need.
I don't get any real free time until June, but I plan to have a few more opinions based on actual experience with the 40 by the end of June...