Hello Saddlesore, and welcome to the Thorn Cycling Forum!
A close look at the Touring hubs on the Phil Wood website shows they are available in a wider range of OLN (Over Lock Nut) widths than the Road hubs and they appear to have "windows" in the flanges.
The Road hubs are available in 130 or 135mm OLN.
The Touring hubs have relieved flanges in the product photos...which *might* be taller, thereby affecting spoke length...but I think not, since each is listed as a "standard flange". You're correct; the front touring hub body is slightly wider than the road body, with beefier quick release caps. The Touring hubs are available in 130, 135, 140, and 145mm spacings.
The MTB hubs have windows like the Touring hubs, but are available in only two OLNs (130, 135) and have the option to fit disc brakes. The MTB hubs can also be converted to a bolt-on configuration for an upcharge.
I presume you're going for the cassette model in each case, rather than the freewheel-specific hubs.
Each of the hubs is available in your choice of 9 finishes/colors.
If 't'were me, and I was buying for a 26" touring bike, I'd go with the Touring hubs...unless I needed to accommodate disc brakes, in which case I'd go for the MTB hubs. If I were going for a road bike or any bike with 27"/700C wheels and needed a front hub, I'd consider the Road hubs.
As a possibly reassuring data point, I have Phil hubs without the FSA (Field Serviceable Axles) dating back to the late 1970s that are still humming along happily with far in excess of 35,000mi/56,000km of all-weather touring use.
Hope this helps.
Best,
Dan. (...who shares a name and enthusiasm for this maker's hubs...but isn't related)