Canon 55-250 IS vs. 70-300 IS
I bought a 70-300 3 weeks ago and I'm impressed with the lens. I can't compare pictures quality but I can tell you that the 70-300 is better built, I was the 55-250 at best buy and thanks to this I decided to go with a 70-300. I keep all my toys for long long time, so better builm for me is very important.
Hope this help a bit.