According to Brandt, solid rims are welded, and box section rims, particularly large crossection ones are likely plugged. He does not express a preference in my edition.
I thought this was one of those luddite issues were the pinned joint is better? My sainted MA2s are pinned.
The 719 seemed on the site pictures to have more of their weight in the braking areas. while the 319 seems to have a tunnel feature for strength but less braking area. It would be of interest if the 719 was better designed for braking and heat absorbtion, as to some extent the milled and welded rims seem to point in that direction whether really neaded or not. The 719 seems to have a 40 spoke option that while it isn't probably what you want, again, is a touring specific rim feature. I got al three of the 719, 319, an Alex DH22 up on the screen and the DH22s that I am running are very similar to a cross between the 310 and the 719. Internal tubes, but deep rim with thick braking surfaces. And the DH are cheap. http://www.alexrims.com/
then search on DH22.
One feature you want is an easy to change tires on rim. Deep usually helps but there are lots of factors. DH22 is very easy to change. You can go like 2000 miles and no flats and then have to change the tire four times in one rainy day.
There are a lot of factors I can't really gage from the slight info rim makers put up, but I would go 1) 719, 2) DH22 3) 319.