Shimano 105 parts vs Shimano Tiagra

From what I see in the Shimano catalog that I got at my LBS… weight is a factor (example: 105 rear derailleur is 231g Tiagra is 280g) From what I’m been told that 105 will take more abuse then lets say the Tiagra… With that being said (I’m sure someone else could rattle off more difference between 105 & Tiagra)

But my take is this:
Buy a bike that is comfortable to her within in the family budget. Now if you have a choice between 105 or Tiagra and the price isn’t a huge difference I would always go with the better equipment.

Note: I would never buy a bike that is for me w/o a test drive around the block…

For what it's worth, a buddy of mine has a Specialized Multisport w/ a 105 rear derailer and a Tiagra front.  He's had all kinds of problems keeping the front adjusted to keep it from dropping the chain.  Keep in mind that his wife has the same bike w/ same setup, so it may be an adjustment issue, but given my buddy's experience w/ Tiagra and mine w/ 105, I'm leary of Tiagra stuff.

I wouldn't go as far as to say they are crap, but they are certainly not of the quality of the upper three teirs. As a number of other users said, it depends on use. For what I assume you want to do you'll want to go with 105 and up. My bike shop won't even stock things with anything less than that for what the site as "reliability issues".

bts

I keep hearing "go 105 or above it is not worth the money to go with Tiagra", but I never hear concrete reasons or what I will notice different about the level of parts. Will they fall apart after a year and I will need to replace them? Will the chain keep falling off? I am sure that 105 is better but before I forkover the extra $400+, I just want to know what I will get for that extra money.

For one 105 doens't have anything plastic. 2, 105 is a lot lighter. 3, 105 will shift a lot more accurately. 4, 105 will take more abuse if you were to take a spill. 5, tiagra brakes are known to be terrible. 6, Don't try shifting on a hill with tiagra, it will likely not shift or the chain will drop. 7. The teeth, a Tiagra Chainring will have it's teeth wear out a lot faster than 105 and if you don't keep up with repairing it you'll ruin your freewheel. These are jsut a few things that I've heard about tiagra components. The difference in quality takes a huge jump when you get into the 105 group.

How much will the bike be used? I got my wife Sora equipment and it works fine for what she does with the bike... Now myself on the other hand I long after a Dura Ace bike but trying to justify $$$$ to my wife is like her explaining to me why she needs all those shoes in our closet But that is another thread.

Ok, thanks for the info.