Neither is better then the other. Both have one useless ability, but both are pretty nice.
Mechanized is good for the early jeep that can counter kubels. you can also go for light armor and use the refund to still rush early mediums. The artillery on it is amazing as well. The M3 is terrible though, don't use it. The commander is great for mobile play and tank rushes.
Armor gives you assault engis to mix up your early builds with so you don't have to do a full rifle opening, but they can be tricky to use right. M10 provides you with a great cheap flanking TD and the 105 sherman destroys infantry quickly, you can also skip major. The arty is a bit situational, but is is great for area denial or if your opponent has a lot of defences in one place. Good luck trying to make use of advanced vehicle crews though. Nice all rounder commander gives you a variety of units and abilities to take on a variety of situations.
I wouldn't say one is better then the other. They both act quite differently.
