In case anyone else arrives at the point of choosing Bento Go or Filemaker Go, this is what I have found out and why I am choosing FM Go:
* Many frustrating problems at present running Bento Go in IOS 5 environment; obvious when reading the Bento Go forums
* In Bento and Bento Go. a field in a related file/db/library cannot be the source of field value lists. (In my case, this is a big pain because it means I must duplicate and update both a data base field in one library and a value list in another. Seems wasteful and stupid-- i.e., suppose you had one db/library that was all about the tools you sell. So the tools are the "key" field and there is more info about each one such as manufacturer, model#, etc. Another db/library is all about your sales; you sell many items, so there is a field that contains the name of the item sold. IF it is a tool, wouldn't it be nice to choose from a list provided by that tool db/library instead of having a second list of tools that you manually update. )
* In Bento, there are no user scripts to do things like generate that "second list" from the tool db/library or some other task that is not inside the box and parameters of Bento.
*In Bento the only computations are Sum, Max, Avg, Mean and very structured in the way you use them
It is a nice package for many applications, and likewise Bento Go will be nice when major bugs are fixed-- more basic and restrictive than FM.
For me, FM is the way to go. There is a 30-day free trial of both. At the end of the FM trial, I can buy the current version for my iMac at 50% off if I also purchase FM Go; the right way to go for me.