Neither manufacturer makes bad parts. When it comes to performance versus price, the mid-range groups from both manufacturers will give the average rider more than enough performance. Pro-level parts like Record and Dura Ace are far more expensive for the modest weight and performance gains they yield, and are best left to the pro's and fashion conscious riders with fat wallets. Chorus, Athena, Ultegra, and 105 are all excellent groups worth consideration. For the rest of the bike, there are almost too many options to mention, so I'll just skim the surface.
Handlebars are also a very personal thing.
Unlike straight ATB bars, there are many different widths, bends, drops, and reaches for road bars. I size my bars by taking a measurement of my shouder width at the joint and using that width, but for average sized riders, a 42 or 44cm bar usually works. If you use clipless pedals, using the same ones on your road bike will mean you don't have to buy a new pair of shoes. Ultegra on my road bike and 747's on my mountain bike, and can use both my road and my mountain shoes with the Ultegra road SPD pedals. Tires are pretty important, too.