V-49,
I just purchased the Trek 7300 and love it! It was easy for me...my wife had done all the research and had just purchased the 7300WSD and was happy with it.
In your case you might go to a dealer who structures the bike specs in an easily comparable way. Our LBS here in Vermont makes that easy, on their web site.
From what I can tell, the 7.2 and 7.3 have different forks, rims/wheels, tires, rear derailleurs, rear cogs, shifters, handlebars, grips (as you mentioned), brake levers, brakes and the seat post. That being said the 7.2 is a great bike, especially for the price.
Good luck!
Cliff in VT