We have done both, most recently (and for the first time) Eagle Pass/Piedras Negras. We enjoyed´crossing at the latter point, but the others are fine too. (I presume you have a stop to make in the Dallas area unrelated to the most direct way to the Texas borders because, coming to and from southern Ontario we avoid going through Dallas because of traffic, etc.)
Anyway, the best place to get up-to-date info about the best crossings at any given time is the Travel Forum of Mexico Connect. You´ll find a lots of great info on the Texas area crossings, including real-time reports from a local in the border area. That´s what we rely on when we travel.
http://www.mexconnect.com/cgi-bin/forum ... t=48086436
"Let your words be few and seasoned with grace". Mother Ann Lee, founder of the Shaker Movement.