I ride a Diamondback Insight 1, and have put over 3000 miles on it. I bought mine slightly used from a LBS, and got a good deal on it. Three years on from its "birth" it's still running just as well as ever. I regularly ride mine for 30 + mile trips, and I still love it.
They're light, comfortable, and quick. The components seems to hold up well, and I've had no real problems except popping a spoke recently after hitting a pothole hard on a paved trail.
The guy at the local bike shop that fitted a new spoke and true'd the wheel, said that the wheel and hub bearings were still in great condition, so I was pleased with that news.

They're pretty good from stock, and the only real modifications I've made to mine are swapping out the seat to one made by Giant (for a little better fit), and adding ergo hand grips (for comfort) and bar ends to give me a change of hand positions on longer rides. I've swapped out the pedals to to BMX style studded pedals to give me more grip, because those stock (plastic) pedals arent great when wet. You'd probably want to do that with any bike you get anyway... we all mod them a little to suit our own requirememnts, right?

I have a Trek 3600, and an older Kent 10 speed road bike (now converted to a cruiser) too, but the Inisght is really my favourite for paved riding.

I've never ridden the other model you mention, but I'd have no problem with recomending the Insight.

All the best!