Canon 55-250mm or the Tamron AF 70-300mm

[JaackBrown]

I already have the 250 but im thinking about selling it for the Tamron AF 70-300mm F/4-5.6 Di LD Macro 1:2 Lens for Canon, this a good or bad idea?

 

[crofter]

Bad idea, you only get another 50mm and you lose stabilization, the 55-250 is a better lens anyway, I had both, the only upgrade would be the Tamron SP AF 70-300 F/4-5.6 Di VC USD but that's more money.

 

[PitaDaVespa]

I've heard the Tamron is a (cheap plastic yet) sharp lens across the hole range, but suffers a bit from purple fringing.
It's also also a full-frame lens.

I guess maybe you could win a bit of sharpness (?) but you would definitely loose IS.

Why would you need the Tamron: 300mm or 1:2 macro?

edit: the Tamron is a faster lens but has slower AF.