Canon 70-300 IS USM vs 70-300 L IS USM

Actually the 55-250 is better than that - in most respects it's almost as good as the 70-300 non-L so I'd give it a 2 or even a 2½.

Before you ask, yes there is a lens in this category which merits a "1". The 75-300 (USM or non-USM), sometimes labelled as Canon's worst lens. Many years ago I needed a long lens for my film SLR and I had no spare cash so I bought what was almost the cheapest tele zoom on the market. It was rubbish but it still doesn't get a zero because it meant I had a long lens for my holiday and that must be worth something.