The original e400s 7501-13 are decent enough and seemed ok with hills IME. However, the Redcar fleet is renowned for its poor condition. After a spruce up, the B7s might be ok but they're 5 years older, been worked very hard, don't have the power of a B9, and there's nothing to suggest that they won't deteriorate in line with Redcar's usual record.
Remember when the Temsas arrived. They were well regarded in terms of performance but are now knackered. Also, internal and external cleanliness of Redcar fleet is dreadful and noticeably worse than Stockton