Those bikes are functionally at opposite ends of the spectrum. The crossway is a hybrid with decent parts and nothing special. The motobecane is an XC mountain bike with high end parts. This is reflected in the price differential. With the motobecane, you are getting a very good deal on the bike/parts, but the caveat is that you have to do all of the assembly and maintenance yourself, or pay a shop to do it. No offense, but you sound like someone who is new to cycling. Frankly, the motobecane is likely overkill and I do not know if you have the knowledge to assemble it correctly. The mongoose could be ok, but would be dissappointing on a long commute (maybe more than 8 miles).
How long is your commute?