My 2006 Volpe is getting a gradual 'upgrade', that being from the original tiagras to the latest version, plus a new rear derailieur.
The left brifter was replaced 2 summers ago after a bike/car collision & now the right one is broken from a wack against the ground. So replacing the right-side will make it complete, but a new derailieur is the real improvement accdg to my mechanic. Overall, he sees that the newer stuff trickles down into lower-end components & so, in effect, I'm getting an 'upgrade'.
Another option we looked at was to replace both brifters with Soras instead of just replacing the right-side Tiagra. This was coming down to 6of1halfdozoftheother. A brand new pair of Soras vs one new (to go w/ one less-new) Tiagra, the prices come to within $20 of each other. I figured that it'd be a waste to have a new pair with a spare left-side Tiagra laying around (though I could have sold it on craigslist or something) so we ordered the new Tiagra.
I wasn't keen on changing to the thumb shifters on the Sora I guess. Other than that, what's the diff?