I think this issue is way overblown. The reasons for choosing a particular string representation in Haskell are analogous to the reasons to choose among e.g. byte arrays, streams, string builders, etc. in mainstream programming languages.
> Which prelude?
There is a standard prelude. Unless you actively choose another one, that's the one you'll get.
> Which compiler extensions?
If you want to use certain advanced language features, enable the appropriate extensions.
> Which testing library?
Many mainstream programming platforms (e.g. .NET) have multiple popular testing libraries to choose from. Is this a bad thing?