I like having the wires trapped under a wedge and nailed down -- we can get quite hot weather here in the late spring and some of my friends have had trouble with foundation warping badly. Of course, if you cross-wire as I have started doing, this is much less of an issue.
Grooved top and bottom bars are faster, for sure. Only seven steps for the top bar that way (not counting cutting them from 2x6s and splitting them).
Lots of fun, an excuse to work out in the shop, which I like. Did 120 end bars the other night, the new bandsaw is working pretty well now that I've got new thrust bearings, filed out the throat plate so the blade doesn't drag on it, and "modified" the back top cover to allow the axle to move up enough to tension the blade.
Now I need to make a drill jig to drill the end bars, buy the eyelets to put in, and finish the top bars, then make an assembly jig and get frames put together -- I'll be needing nuc boxes by late March.