Quesiton about ohms and subs

Neither one is necessarily "better" or "worse".  Each version is better suited for particular setups.  I'd say in most situations, the dual 2-ohm version is a little more versatile just because there are so many more amps out there that can run a single 4-ohm load, than there are amps than can run a single 2 or 1 ohm load.

The dual 2-ohm version can be wired up as a single 1-ohm load (voice coils in parallel) or a single 4-ohm load (voice coils in series).  Not many amps can do a 1-ohm load, but most 2-channel amps can be bridged to a 4-ohm load to maximize their power output.

The dual 4-ohm version can be wired up as a single 2-ohm load (voice coils in parallel) or a single 8-ohm load (voice coils in series).  Two 4-ohm DVC subs together though can be hooked up for a single 4-ohm load, for using with a 2-channel amp's bridged outputs.  So if you have a 2-channel amp and two L7s you'd probably want to get the 4-ohm DVC version.   If you intend to have just one L7 though, you might be better off getting the dual 2-ohm version.