Originally Posted by Brian Ratliff

Downtube is more reliable. It is a proven, if old school, solution. Sora thumb shifters, where it is nearly impossible to shift from the drops, have a skill level ceiling (as you advance as a cyclist, you will be forced into an upgrade). Downtube does not. Plus, with downtube, it is really easy to move to more modern components fairly inexpensively (9 or 10 speed drivetrain).

Neither bike is something to plan upgrades around. Personally, I'd keep the $50 in my pocket. Buy for absolute cost and reliability rather than value in this case, since value of both is fairly low. When going cheap, it is better to put your money on reliable old tech rather than shtty, cheap versions of new tech. Sacrifice features in order to keep quality higher.

Seems you get a better fork in the deal as well for the downtube shifter bike.