They will all be of comparable quality, using many of the same parts, with the higher priced models probably having slightly better parts in a few places.
They will have slightly different geometries, so some may be more comfortable to you than others.
And you may like certain bike shops better than others.
I would go with the one that has the best combination of riding comfort plus your confidence in the bike shop. If you go Trek, then I would lean toward the 7100 over the 7000 due to better overall parts quality.
i will be using the bike on bike path ridng with my wife 15 - 20 miles. i also have a road bike for longer and quicker rides.
I would get the one more suited for off road riding, I do not have time to go through all the specs of them, but some are more for road riding . Smaller tires, no suspension, etc...you said you had a Road bike, and this would be used for off road mostly... Richard