Hi,
I can highly recommend the Motorola Defy plus as a bike smart phone.
There is no right answer to your question about what is best, it is about what you need.
The big advantage of the Defy is it is water proof so you don't need the additional water proof case. I use an aluminum case cable tied to the stem which provides good protection. It isn't much bigger than a Garmin 800.
Battery life is very good. Compared to previous HTC phones which would not last much more than 4 hours, it gets over six with the screen on.
Which app you use is down to personal choice. I use RunGPS which works well with Bluetooth heart rate monitor. The screen can be customized in many ways with any data you want (speed, distance, altitude etc) and all kinds of free maps including OS.
I can post a photo of the case set up if you like.
It is average as far as phones go in terms of speed etc but is a good compromise.
Regards