JVC kaboom vs Ion portable ipod speakers for pool parties

I'm wondering which one would be louder/better sound quality. I'm not that picky on the sound quality, but it has to be decent. I'm mostly going to bring it to open air pool parties or the beach.

The JVC rv-nb1 or rv-nb20 look good and are around 20lbs.
The blockrocker is 40lbs (so I figure it might be louder), but maybe some of that is because of the rechargeable battery.
http://www.ion-audio.com/blockrocker

Can I use rechargeable D-cells on the jvc ones? Is their battery life good?

Any other suggestions?

I did find out the R1 is the old one. The nb20 doesn't have a tape deck and has a ipod port not Ipod dock. I ordered a nb10 and $100 worth of rechargeable D cells