I've google'd and researched but I still don't quite get the difference between the Shimano Ultegra, Tiagra, 105, Sora, etc.

What exactly does the other do better? I've seen 2012-13 bikes with Dura Ace and wonder, "why didn't they put the newest one available?"

Sorry if this question has been asked or I posted in the wrong section.

Cheers.

Generally the more money, the lighter weight and more longevity. Usually when new things are introduced like electronic shifting and 11 speed, it goes to the top end Dura Ace first and over time works down to Ultegra, 105, etc. So what you see in 2013 105 components, they might have been 2011 or 2012 Ultegra with a different label (perhaps with some other minor changes)

Not so always. Some higher end parts will wear out just as fast if not faster.

Sora is 9 speed, everything else is 10 speed, as you go higher up, parts weigh less and less, although the difference isn't huge, the feel is said to be slightly better in the better components (duraace is the highest, then ultegra, 105, tiagra, and sora, and 2200) people tend to state that 105 is the best bang for the buck and "good enough" for racing, hell I took my Tiagra racing, 25th out of 60 racers, collegiate level, having a duraace equipped bike wouldn't have propelled me to the top of the peleton. Having a well adjusted shifting system would make a larger difference than the component levels. $30-35 for a nice set of jagwire cables every half a year would yield better results than running the higher up groupset with cable changes every year instead.

Debatable. Other than that one would likely take better care of a Dura-Ace equipped bike over one with Sora, how do you figure the more expensive Group will last longer? In fact, I'd dare say that the consumables on the higher end have a much shorter life than the lesser priced ones.



More dollars will get you lighter weight, more precisely machined parts (which amounts to better, more precise shifting) and, of course, the Bling that only Dura-Ace, Super Record, and Red can add to your bike.

Sora will shift better than Dura Ace, if it's been set up 'better'. I think anything over 105 'level' is overkill for racing on a budget (I race Sora due to budget, hasn't let me down at all). But, if you're budget is ever-ending then sure, why not have the best equipment you can buy/afford? People who spend that much probably won't notice the extra money and *feel* better about their bike and it's performance. Win/Win.
I can't comment on longevity, I'm relatively new to brifters, I've only rode MTB and Track before last year.

In the case of Ti cassette cogs, they will *definitely* wear out faster.

Definitely.

I have been on SRAM for awhile, but when I was riding Shimano I felt like the best value was DA shifters and crankset; Ultegra RD, cassette, and chain; and 105 everything else. Maybe it's different now.