The Trek is much smaller ... and much cleaner. You can tell a shop or an enthusiast really wants to get max money for it. Nice detailing. The bike looks ready to go, the paint isn't all chipped and scratched (that i can see) which tells me that the the bike wasn't abused. The tires look pretty pavement-ready (as opposed to the C'dale's knobbies.)
I'd say either one for $150 would be a good deal (the C'dale needs pedals but you could get junk pedals form any bike for a 3-mile commute.) Caveat: I cannot See either bike, I cannot touch either bike. I cannot pick up and shake either bike, or bounce them, or spin the tires or shake the cranks or squeeze the brakes or shift the gears .... either of these bikes could be junk.
But the biggest thing is fit---the Cannondale looks huge (those cranks look like clown-shoe cranks) and the Trek looks tiny. You will not ride a bike which doesn't fit .... you will not be abler to comfortably ride a bike which doesn't fit.
The Trek has obviously been gone over by a shop mechanic and probably comes with a warranty. The C'dale might have been sitting for who knows how long so it might need some work or it might not. Also, it looks as though the C'dale has off-road gearing---pretty low gears. I cannot tell without looking much more closely. (On closer inspection it might be 48-38-28---hard to tell the scale, but not an issue after all.)
I think the Cannondale is overpriced. it is an old, old bike but not a terribly desirable bike. But, if it fits and you want it, you have to make whatever deal you can.