Cant speak to Sora, but Tiagra is just fine and well made. I did replace the mechanical TRP disc brakes for hydraulic Tiagra brakes. Huge upgrade. Getting true hydro brakes would be a valid reason to get Tiagra or 105 over Sora. Hydro is expensive tho.
I used to ride the older 105 5800. I have no recollection it was any better than Tiagra. If anything, it was more finicky adjusting the gears. The Tiagra crank is a boat anchor, but so is many of the non 105 cranks that is on oem bikes to save $. Imo weight is overrated anyway. You wont notice except when actually carrying the bike. I never missed the one gear compared to 11s 105.
Last edited by Racing Dan; 08-22-21 at 10:59 PM.