Choosing an Audio Interface is one of the most important decisions I've made on purchasing hardware for my studio. I have been through 3 audio interfaces now and noticed the difference in sound quality in each one. All producers who are just starting out will have to make a decision of which audio interface to invest in, so I am going to share my experiences and advice on what to consider.
The main things that come into consideration are budget, size, mobility and sound quality. If you are deciding what interface you should go for, the first thing to ask yourself is how far do you want to take your music productions. Maybe it starts out for fun and turns into something professional, or maybe you are at the point when you want to release professional productions on a monthly basis.
If you just want something decent that does the job, don't want to spend too much money and fair enough, there are many audio interfaces you can purchase for about $100 - $200 that will support Asio, 24 Bit, 96 KHz, External USB, Headphone Jack, Low Latency, 2 Inputs and 2 Outputs at the very least. That is probably all you need, or maybe 4 ins and 4 outs to plug in some hardware. This is what I thought I needed about 10 years ago, and so I purchased an EMU soundcard which supported all these features. It was a great improvement from my previous soundcard, and it was all my budget could afford at the time, but I was never really happy with the card.
I experienced a lot of glitching while producing, especially when my tracks got full with loads of channels and VST's. I experienced far too many crashes due to latency and lack of memory & cpu power needed for the project sizes (to be fair I probably had a lot of plugins and channels that were not needed).
I decided to save up some money for a really really good professional sound card. When I eventually had the budget I invested in the RME Fireface 800. It is discontinued now, but it's still one of the best things I've ever bought. I would have preferred the new model as I knew the Fireface would be discontinued, but again, it's what my budget could afford.
I have not had any problems with the card to date and it's almost 3 years old. It comes with some really nice software for frequency monitoring, and has enough inputs and outputs I'll ever need for any size studio. The sound quality is amazing, the quality of my productions improved drastically. With RME, you get what you pay for. In 3 years, I've had maybe 2 or 3 crashes. I save regularly so I don't remember loosing anything important. I was so used to crashes that I just got into the habit of re-creating what I lost.
I would always advise to choose an RME interface if you can afford it, because I know how the soundcard helped me improve the quality of my sound.