yea,42r have the longest battery life for shure. I haven't tried many 42r firmwares,but all I can say is that 42r is the best. On second place is 46r and on third 48r
1. 42r - best sound quality (wich I think is the most important thing on e398/e1), longest battery life and best stability, aldo the speed of firmware is so slow,but I can handle it
2. 46r - the fastest one, that's for shure, you can't say that it's not, sound quality can be also very good, almoust comparable to 42r, very stable firmware and very good bat life. only thing that is bad is auto delivery report patch,which actually doesn't exist
3. 48r - is somewhere between 46r and 42r... I haven't used it so much,but it's better then 49r
I hate 49r because of sound quality... It's only good for paching, but I need only 11 paches so....