Miltech (Army Reserve) vs Dual Status Technician (National Guard), which is better for career progression?

Lots of factors involved.
It's stated above that the guard will have fewer mil tech's, I see that as a positive. They are making those positions civilian and your job will no longer be tied to your reserve service.

The Guard’s Miltechs currently have a bit better payscale, the other piece is the Reserve’s military structure is better, so while you may be a lower WG, your progression throuh the ranks in your unit is better. The Army Reserve is working to get their WG and GS structure upgraded. The MilTech program is dual status, and there is some ability to move from one to another. USAJobs has the advertised positions. It’s a great time to get into a MilTech position

Great job for a young soldier, once you gain experience and max out your WG level 5, it becomes a dead end job. You can make much more money in the civilian life at that point. As the only raises will be from what the Pentagon gives you. The last 6 years had been 1 percent give or take a few additional points.