I think go for the bike with the cheaper parts to start. It'll get you hooked, and eventually you can either make a better upgrade (Ultegra or up) or just get a whole new bike! The 105 stuff is a bit lighter, but I wouldn't say it has a much longer life then the entry level stuff. I put more than 15,000 miles on a sora/tiagra bike with minimal mechanical problems. Just keep it lubed, and clean.
good luck!
bill

Check out the site www.roadbikereview.com. Look under the section reviews and then groupos. It will give you many user opinions on the different shifting systems.

If you are interested in road bikes and you believe you may ride it for years, also check out www.trekbikes.com and look at two entry level models - 1200 and 1500. They retail for about $1,000 and are highly rated by user reviews on the site above. I got hooked on Trek because of the lifetime warranty on the frames. The company has been very good to me over the past 12 years. Trek replaced a ten year old frame that cracked with a new frame and on another bike they repainted it because one decal was peeling off. They did it very quickly with no cost to me.

Good luck,

I'd recommend sourcing a bike that has Tiagra shifters which are 9 speed v. 8 with Sora. With 10 speed bike parts in full bloom (Shimano is releasing 10spd group for 105, the next level up from Tiagra this spring), sourcing and choice of different 8 speed replacement parts, i.e. various cassette combos, chains, shifters, etc. will be a bit more limited than 9 speed, if it is not already the case. You may find the Tiagra shifter design to be more favorable, too. The incremental cost of Tiagra over Sora should not be that much.

I would go for 105's anything lower then that will not hold up,
and only have to be upgraded later. It seem you have weight so I would be concern with the stopping power.
Another way I look at it would be who gets dropped!
Lets say all things are equal the same weight, the same bike.
but one has 105 and the other has sora/tiagra.
Its time to change gears 105 will change smoother and sure.
sora/tiagra may miss or drop the chain in the wrong gear you have to reshift to get in the right gear.. but now you are dropped and have to work to catch up.
Just my .02
I hope to see you out there

From what I've seen, the lower level components perform quite well, but may not hold up as long as the higher end stuff.

Over time this may mean that shifting gets sloppy or that parts fail out on the road.

I've got 2 bikes with 105 and one with DuraAce. All perform just fine. The 105 has a softer feel in the shifting, the DuraAce is crisper. Barring a crash, I expect they could outlast me.

I agree with the views here.
Go Shimano 105 or up.
You will not regret it.

10 speed if you can afford it, otherwise look for good deals on 105 9 speed bikes.

I have a Cannondale R500 with Tiagra shifters/brakes and front derailler and 105 in the back. It works pretty well though shifting can be a little clunky. I realized this when I rode a full Dura-Ace bike that shifts like butter in comparison. Aside from the clunkiness and some squeeking my combination has held up well in its first 500 miles. A bike mechanic told me he sees lots of Sora components needing repair in his shop and recommended at least Tiagra to start. Go with what you can afford is the obvious answer.

" >>Any thoughts on the most economical road bike with 105 components?

That is not a good approach. The most important thing is a frame that provides a good fit and ride. Components can be replaced if they wear out. The frame can't (well, not easily).

Choose a bike by how it fits and rides. Components are secondary. Tiagra/Sora are ok to get started.

""Chainwheel"""