Originally Posted by
spectastic
I know for shimano and campy, there are generally 5 grades in quality: sora -> tiagra -> 105 -> ultegra -> durace.
That's the wrong perspective. You have enumerated five price points meaning how much you'll spend. You have not specified five levels of "quality".
But I have heard that for 105 and up, the components are actually less durable and are more geared toward light weight and speed. Is this true?
Also wrong. There are five price points there. Durability may increase (Dura Ace does have better alloys), decrease (titanium cogs last half as long as steel), or stay constant and regardless it might not matter (I got 15 years out of my last rear derailleur before I needed to pay attention to getting enough over shift moving to larger cogs due to upper and lower pivot wear). Quality may go in any direction (Carbon clear coat is much easier to chip than hard anodizing, cold forging with Dura Ace produces a nicer finish than hot, and a lot of the Campagnolo small parts were identical from Record down). You'll probably loose a few grams which are generally irrelevant (unless you have body morphology conducive to climbing fast as suggested by weighing about 2 pounds per inch or 140 pounds at 5'10, stick to a decent structured training program, have OK genetics, and do road races in the mountains...)
How much weight are we talking about?
Maybe zero. Campagnolo Ultrashift levers weigh the same 337g per pair whether you buy Centaur Carbon, Athena Carbon, Chorus, or Record levers. Maybe a tiny amount - Super Record saves 7g per pair (enough for a 140 pound climber atop a bike formerly that far above the UCI minimum to save 0.36 seconds per hour he spends off the front climbing to a mountain top finish). Most definitely not enough for you to care (if the same rider and bike combo were 300g heavier as was once the case comparing something like a solid alloy triple crank and carbon double but now days can capture the difference between a few group levels he'd loose 0.4% of his speed which could cost him 15 seconds on the chasing peleton that does matter; although you finishing your workout in 1:30:15 not 1:30:00 does not).
Also, there are other components such as wheel hubs and bottom brackets that aren't named in this grade system. Is it just because they're generally the same, and there's not much to distinguish?
Maybe they're the same for all practical purposes. 2000-2006 Campagnolo Centaur/Daytona, Chorus, and Record hubs were identical apart from the grease ports on Record hubs, titanium pawl carrier which saved 10g for Record, and quick release skewer. The Record part is the sexiest QR skewer ever made and NOS pairs sell for over $140 on e-pay which might matter to you, but you should be honest about it "Damn! That thing is sexier than my wife in her new high heels!" instead of justifying "I'll save 10g" which would gain 0.5 seconds on the chasing peleton when you're racing off the front to a mountain top finish assuming you weigh 140 pounds and that drops you to the UCI minimum bike weight.
Maybe they aren't. Current production Campagnolo shifters are crippled when you buy less than Chorus level (which nets 5 cogs smaller versus 1 below). Hubs below Centaur/Daytona got cartridge bearings until 2006 when only Record got the good stuff. Rear derailleurs below Chorus got a C or E clip attached to a stud instead of a screw to attach the cage which is harder to disassemble and easier to loose.
You need to evaluate this on a component-by-component and year-by-year basis. In some cases less (steel big cogs which last twice as long as titanium) may be more. In some cases the aesthetics will dictate.
For most riders in most situations the differences are limited to cosmetics and the positive effects you get with placebos.