When comparing Swift vs GemStone/S, the Slant community recommends Swift for most people. In the question“What are the best server side programming languages?” Swift is ranked 19th while GemStone/S is ranked 25th.
Ranked in these QuestionsQuestion Ranking
Pro Modern syntax
Pro Swift is closer to other platforms
Apple’s modern programming language is easier to understand for non-iOS developers and minimizes time for additional explanations and clarifications. Moreover, Swift can be used as a script language. It is an interesting solution for the iOS community to unify writing of build scripts. At the time being iOS developers are split up in regard to this activity. Some of them write build scripts in Bash, others use Ruby, Python, etc. Swift gives an amazing opportunity to be applied to all iOS programming needs.
More details can be found here https://mlsdev.com/blog/51-7-advantages-of-using-swift-over-objective-c
Pro Works with Apple's Cocoa and Cocoa Touch frameworks
Pro Can be used as a Just-In-Time language
Pro Inherent parallelism
Pro Low memory footprint due to reference counting
Pro Backed by Apple
Pro Performance speed comparable to native C
Pro Swift has some clever tricks up its sleeve
Due to having elements of a functional programming language. Things like 'map' and 'filter' for example.
Pro Uses LLVM compiler and Obj-C runtime allowing C, Objective-C, Objective-C++ and Swift code to run side by side within a single program
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
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
Con Swift is a moving target
They've released 1.2 so far, and 2.0 is coming soon. Every small update brings adjustments to paradigms (such as how to do type casting) that can be a little frustrating to absorb. Objective C was also constantly updating, however, but not at the same rate these days.
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.