Been on both a good few times, B5LH has an unconventional downstairs layout but overall has grown on me. The initial start up is sluggish under the electric power till the engine kicks in and intial gear change occurs but it is very impressive speed wise when it gets going. Considerably faster than the Enviro 400H although there has been only one time I've experienced it as usually the 22/23 is a fairly congested route. I've read reviews that have suggested it's performance on routes that allow the B5LH to get up to speed it's superior to an Enviro 400H. Although the 400H seems to perform much more like a traditional bus on stop/start urban routes, from what I've heard it has quite a low top speed and can struggle on out of town, hilly routes in comparison with the B5LH. Can't find the review I remember reading but this one is quite a decent read
http://www.focustransport.org.uk/fhybrid3.aspx
http://www.focustransport.org.uk/fhybrid3.aspx