I've read a lot on keeping them rear facing as long as possible. That was the main reason I stumbled upon the One4Life. It says its rated for up to 50 lbs rear facing vs the BLVD is rated to 40 lbs.
I haven't read much on Diono, so I'll do that this evening
I should make sure to mention - the One4Life wasn't an option five years ago when we got our last seat. If it does 50 lbs RF, that's really good, and should definitely be looked into. I can see if I can find a site that isn't ads comparing the two and post it - it sounds like a great option. That would be higher than the Diono (last I knew, they went to 45 lbs RF). My children were teeny tiny, so we never had to worry about hitting the weight limit RF (my 6.5 year old is still not 50 lbs), but that is hard to predict when you're first buying!