When comparing Snap vs IHP, the Slant community recommends Snap for most people. In the question“What are the best Haskell web frameworks for building RESTful web services?” Snap is ranked 7th while IHP is ranked 10th. The most important reason people chose Snap is:
Snap provides "snaplets". These are self-contained modules of code that provide additional functionality without muddling the core library. Having these resources saves time when developing code.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Provides modules for changeable functionality
Snap provides "snaplets". These are self-contained modules of code that provide additional functionality without muddling the core library. Having these resources saves time when developing code.
Pro Easy for beginners
With the code generators even haskell beginners can easily build CRUD apps.
Pro Under the hood
Code generators, database schema editors, etc. work with Haskell and SQL files, which can also be edited manually, to get 'under the hood'.
Pro Instant live reloading
Makes for a super smooth development experience.
Pro HSX
If you have experience with react, you feel right at home with the HSX view syntax.
Cons
Con Outdated documentation
The comprehensive Snap documentation is currently outdated (last activity appears to have been 2013), though Snap itself is under active development. Note that this primarily affects tutorials and guides; the API documentation is generated automatically and remains current.
Con (Small) Server deployment
I'm a bit unclear on the memory requirements for the server (which becomes less of an issue every following year).