First, the vast majority of audio recorders now record either to WAV or MP3 format. The smaller voice recorders (like your Olympus models) may record to some other format, but any good quality recorder will do both formats. For the best result stick with WAV, but for long recordings MP3 works fine too.

Second, especially in a journalism application I would suggest getting a recorder that has the ability to record in 360 degree stereo. not all recorders do this. The Zoom H4n is kind of big, but it has the ability to record in three different patterns so that you can pick up only the audio that is important to you and not record much of the background noise. Also, if quality of audio is important to you, the bigger the microphones are the better.

Lastly, always go for a recorder that uses removable media. That way if you are half way through a recording session and run out of space all you have to do is slap in another card.

I’ll admit, I have a passion for these things. I have actually done hands on testing and presentations on a large number of audio recorders. If you or anyone else is interested in them take a look at the guide I put together on the topic:

http://www.musicedmagic.com/audio-video/portable-digital-audio-recorder-buying-guide-with-reviews.html