My friend has an iRiver HP 120 and it works fine and I honestly like it better than my cousin's iPod equivalent of the 20gb player. Anyway as to your choices, I would suggest the iPod mini even though it is 60 more bucks since you do get more space and honestly, when will you really use FM tuner and voice recording? What for? The bad thing about the iPod mini is that the battery is not user replaceable unlike the iRiver iFP-799.

You can check out these sites for reviews:

iRiver iFP-799
(Make sure to click on the link for iFP-790 since they are practically the same thing)

Apple iPod Mini