Why would you use one vs. the other for back-end development?

Two Answers... MOST PEOPLE ... Choose what they know best as the language solution. I could bet money that if you did a poll asking both: 1) Which language do you know best? ... and ... 2) Which language would you choose? ... that there would be a 95% correlation between the 2 answers. THINGS WE SHOULD BE ASKING: 1) Is the expected lifespan of the desired language good? (If you have to have to rebuild in 7 years, then either your language, or more likely your application architecture (or Software Architect) is broken. 2) Is the language supported by a good library base (connectors to different databases, etc). 3) Does the language or its libraries have significant characteristics important to your application which are not available in other languages (i.e. set based processing of SQL for reporting productivity) 4) Does the language support the desired environment characteristics. (RAM usage, response times, CPU requirements, scaling, ...) 5) Is the language supported by a good experience pool? (i.e. can I easily hire new people to support it, and the associated things it may also require, like IIS or Apache) 6) Is the language going to unnecessarily increase the required breadth of skills for my organization? (more important for smaller organizations) 7) Cost of ownership - Includes things like: cost of rebuild? Do I have to maintain an additional developer skillset? Do I have to maintain additional hardware/OS/Web stack? Do I have to maintain an additional hardware/OS/Web skillset? (the actual build and new hardware costs are often less significant than ongoing maintenance of the required people resources) 8) ... yes, I'm sure there are other items I missed ... SUMMARY: Often, (and likely in this case) looking at these larger picture items, the answer is "It doesn't matter", assuming the languages being compared are mature, robust, and purvasive, which they are in this case.