hard to say, sony hasn't been in the camera business for that long, tamron has been there longer. yet i am looking into getting a sony pocket camera, 30x optical, so i guess they must know what they are doing. i do know that tamron does vary.
the 28-300 - terrible lens.
the 28-300VC - slow but very good, it's what i use for everything
the 28-75, is almost prime quality, fast, nice good contrast, good walkabout lens, i use it as a backup.
---Mike Savad