Really the only difference is materials. The bikes we recommended are full CrMo, which is lighter and can provide for a less springy ride than hi-ten. Honestly tho, every bike under 300 bucks is gonna basically be the same, geometry differences aside.

My biggest issue is that if you buy a 300 dollar bike, you're almost guaranteed to have loose ball hubs and headsets. Which means that as you ride it in the dirt, you're going to be filling those bearings with crap that has to be regularly cleaned out. More expensive bikes will have cartridge bearings everywhere, which require much less maintenance.

Consider going to craigslist and finding a conversion. '80s road bikes usually have huge clearance for tires and fenders. Buy a better bike later with the money you saved.