I have both installed but end up using jRiver more than foobar. Foobar I will say is second best as it is very light on resources/is very snappy if used without skins/tweaks. JRiver on the other hand is a very vast audio/video player with many features (I barely use any) but I like the fact that they have a 64 bit version and I could not find any audio 64 bit player. It probably makes no difference in real world usage. It sometimes ends up playing video files are not playable even in VLC and this actually blew my mind!
With stock settings both sound same (to me) but in JRiver if you do the following:
1) DSP Studio>Equalizer>Rock.
2) DSP Studio>Effects>Environment>Recording Studio
3) DSP Studio>Effects>Environment>Virtual Subwoofer>6"(or whatever you like)
4) DSP Studio>Effects>Environment>Surround Field>Maximum Enhancement (or whatever you like)
... these settings make jRiver sound very musical and enjoyable as compared to stock foobar.
With these settings the sound is probably not pure/true/accurate and is "colored" as they say but it really sounds good and I just sit back stop typing/do anything and just enjoy music