The Tamron, Sony and Sigma lenses are all in the same sort of category and will all offer similar results..........all perfectly good and very acceptable unless you push the lens to it's limits..........avoid the widest and narrowest apertures and you will be well pleased with any of them.....I have always had a soft spot for Sigmas, but for a different reason, being that the "throw" on a Sigma when twisting to zoom or manual focus goes in the same direction as my Pentax lenses whereas that on the Tamron goes the opposite way.........TD always likes to make things easier if he can and does not want to have to pause and think about which way to shift the barrel.
As you can see from unkyUb's photo., these lenses do extent a fair bit when on max. zoom...............if you then set to the macro mode on them, they will come close to doubling that length and can be a bit of a handful.....tripod essential.
Macro mode is handy as unkyUb says............on these lenses you will get a ratio of 1:2.......half size objects.