When comparing GemStone/S vs Crystal, the Slant community recommends Crystal for most people. In the question“What are the best server side programming languages?” Crystal is ranked 24th while GemStone/S is ranked 28th.
Specs
Ranked in these QuestionsQuestion Ranking
Pros
Pro Scalable object-oriented persistence
Gemstone/S is a persistent object environment, capable of high performance database tasks.
Pro Free version even for commercial use
GemStone/S has very capable licenses for no cost that allow businesses to use it commercially for no cost.
Pro Extreme robustness, performance and flexibility
This product has a long line of evolution, guaranteeing all these qualities
Pro Smalltalk
Smalltalk is one of the most productive environments, which makes the hard things easy and the difficult, practical.
Pro Tightly related to Pharo Smalltalk
You can develop your Smalltalk projects on friendly Pharo and run them on the rock solid GemStone environment.
Pro Live debugging production errors
Never debug from textual traces anymore: do live debugging of saved stack traces for production errors
Pro Elegant syntax as Ruby
Pro Fast performance
Pro Has co-routine
Pro Compiles to native binary
Cons
Con Vendor lock-in
The environment is unique and you easily become very dependent on what it has to offer, while there is no alternative vendor to switch to.
Con The runtime environment is essentially free, but not open source.
Con Aruguably no better than a meme language
The elitest attitudes in the community are unwarrented. Not recommendable for production use. Poor error messages, odd compiler errors, poorly documented behavior, etc..
Con Small community
In regards to its age and already past 1.0, the community is still too small.
Con Not cross-platform
No official Windows support.
Con A language only Ruby fans can love
Ruby-ish language.
Con Slow compilation
Con No parallelism (yet)
Not actual anymore.