C# or Java

Hi,
I want to learn either C# or Java. But I don't know which. So /prog/ please compare the two language for me. Language features/how well it is designed/etc. are the things which interest me.

I'm using Haskell at my startup presently and have used it for contract web development in the past (with great success).

My startups product consumes soft real time energy usage data being pushed every second from our customers homes. The daemon is written in Haskell, it buffers into a memory backed acid state store. If there are any subscribers to the channel it will also publish using redis pubsub on a channel for that device. This is used for a web socket implementation to display that data to the user as it's updated. The websocket server that listens to redis pub sub is written in erlang so I could leverage Sockjs (which doesn't have a mature Haskell implementation yet).

Every 60 seconds a reaper also written in Haskell, reaps the data from acid state, computes change over time and a few other things we need then pushes that data to tempodb (the api wrapper I also wrote in hs).

We use Haskell elsewhere too but it's trivial.

This piece, combined with supervisord, has been rock solid. I dislike programming in python now and wish I could rewrite our entire web app with hs but that's too big for just me at the moment...

Since early 2013, we at IMVU have used Haskell to build several of the REST APIs that power our service.

When the company started, we chose PHP as our application server language, in part, because the founders expected the website to only be a small part of the business! IMVU was primarily about a downloadable 3D client. We needed “a website or something” to give users a place to download our client from, but didn’t expect it would have to be much more than that. This shows that predicting the future is hard.
Years later, we have quite a lot of customers, and we primarily use PHP to serve them. We’re big enough that we run multiple subteams on separate initiatives at the same time. Performance is becoming important to us not just because it matters to our customers, but because it can easily make the difference between buying 4 servers and buying 40 servers to support some new feature.

So, early in 2012, we found ourselves ready to look for an alternative that would help us be more rigorous. In particular, we were ready for the idea that sacrificing a tiny bit of short term, straight-line time to market might actually speed us up in the long run.

http://engineering.imvu.com/2014/03/24/what-its-like-to-use-haskell/

In Picus, we built our network security assessment and monitoring product using pure Haskell.

At Silk we've been using Haskell for all our backend (non-browser) code for over four years now. We have an irregularly updated engineering blog:
http://engineering.silk.co/