As I understand it, the PowerCube batteries are for high amp-draw situations; when you have a power hungry HD camera, maybe transmitters, lights, motors, etc. pulling more than 6amps. Those batteries are rated for up to 10 amps or something like that. At the time that Tiffen had IDX produce the PowerCube for them, the HL9 was not available - and possibly that there wasn't a high-draw battery option available in V-Mount. I will probably be corrected on this if I'm wrong. The IDX HL9 (http://www.bhphotovi...on_V_Mount.html) is comparable to the PowerCube - but even Tiffen has told me they aren't in the battery business and you can probably find cheaper alternatives.
The Endura-10s batteries will actually last longer than the PowerCube if you're pulling less than 6 amps. The E-10/E-10s last longer, but won't handle a high draw, over 6 amps.
PowerCube - 88Wh, 6.15Ah - 10amp cont. draw
HL9 - 88Wh, 6.15Ah - 10amp cont. draw, stackable
E-10/s - 93Wh, 6.3Ah
There are, of course, other brands available - but I cannot speak to them as I have no experience with them. I own 4 of the PowerCubes since they came with my Archer2 rig. I'm buying E-10s batts for normal use, and keeping the PC for live TV use when I have a large camera, transmitters, etc.
My 2 cents, buy the HL9 if you want to keep the same capacity. The HL9 and E-10 can stack, but there aren't a lot of situations when you'd need to stack on a steadi-rig.
As for the 24v cams, I haven't shot with one yet. As I understand, film cameras run on 24v, but I'm in the digital world.