which subwofer is better?

They're both better. The JL line is generally a bit tighter and a bit more defined than the old DD Velodyne.

I had a 113 on loan for a few weeks and I owned the DD18. My main speakers are Avalon Acoustics Eidolons. Using their internal EQ I never got the JL to blend with my room and speakers. Its speed and definition always drew attention. Using the Velodyne EQ on the JL helped but it just wasn't a match. Even so the JL is a beautiful well made sub.

I've since moved on to a pair of Velodyne DD-12plus which have been substantially redesigned over the original DD series.

All fine subs. REL units in general are excellent and many dealers will say particularly good for music. I don't think you have any downsides with any of these options you mentioned. Just have fun with the process :-)

probably get more head-room and punch at high volumes with the JL subs. I sold Rel in past, which are very musical subs - Not so much slam and power with HT rocking, though.
Personally, I like the combo of musicality and HT slam factor of the Paradigm Servo 15 for cheep money, in a large room. The Earthquakes also fill a huge space, take lots of power, and are pretty tight when setup correctly.
As with ANY sub, however, your main issues are getting the subs set up in the room properly, in relation to the seats and speakers. Get phase wrong, or sit where there's big suck out in the bass, big bass humps and imporperly mated coherence with the mains and it is all a moot point! You'll never have great bass performance...just a big sonic mess of over-bloated bass engery, that's got lots of issues, and negatives, rather than fast, tight, dynamic, extended, coherent bass with slam and seemless integration.
I'd say 3/5ths of the performance is acoustics and setup with the sub (EQ'ing?), and the rest is design of the sub itself. That's bass for you....

Avgoround wrote:

I'd say 3/5ths of the performance is acoustics and setup with the sub (EQ'ing?), and the rest is design of the sub itself. That's bass for you....

I'd say 80%, but that's really just me agreeing with AVgoround and adding a little nitpicking for fun.

If you use Audyssey (or equivalent DRC) in your HT electronics, I'd go for the JLs. They go clean and loud better than most. If you do not have DRC in your HT electronics, I'd go Velodyne DD, which includes the same functionality in the sub's set-up software.

BTW, the Velo DRC is IME rather primitive and MUST be set up manually.
Marty

You need to take the power delivery to your system into account. If your system is on (1) 15 or 20 amp circuit, you'll need another (as in dedicated) line if you want (2) subs like the Fathom 113s - they are 2500 watts each.
I sold my Fathom 112 to a friend and went to (2) James EMB-1200s, because I wanted stereo subs without adding a dedicated line.