I've owned all three generations of ES, and while this third gen (2010 to present) is, IMHO, a better, more natural "acoustic" tone than its predecessors, the previous-gen 9v system is no slouch. The most significant tonal difference is in the mids where the older version needs more mids attenuated to sound like an acoustic guit (and less like a magnetic pickup like electrics), and the current ES is voiced such that you need very little (if at all, depending) tone sculpting; it's that good (again, IMHO whereas many do not care for the ES tone, which I won't go into here). You have a good ES. If you got around 2 bills to burn and/or you're more finicky about your live tone, then you can easily upgrade your system to the present ...a bit OT, but thought i'd just drop that in your ear as I have done two guits to date as that is how much I like it
As for balanced vs unbalanced, try this :
http://en.wikipedia.org/wiki/Balanced_audioThe gist is you get a better signal-to-noise ratio, superior noise rejection (e.g. ground loops or RF), and increased cable length will not degrade the signal.
As for why I went from balanced to unbalanced it's simple: I gained nothing from an already clean signal and great tone. This and the fact I use an LR Baggs Venue and, again, running balanced to the unit offered no better tone, just more signal (which I did not need). In fact, that hotter signal overwhelmed my previous Baggs PADI, and I've likewise seen other units (especially acosutic guitar amps) whose input pad is not stout enough to "gain down" that very healthy signal, which results in your turning down the ES at the guitar waaay low, and sometimes even mild distortion because you're overdriving the input. And it depends on what system you're playing through. As I had mentioned, it's important to try it different ways, be objective, and determine which works best for you. And for me, simple setup/teardown and the most direct (and again, simple) signal chain is better so long as the tonal results are good. So if more complex yields no practical improvement, then why bother. FWIW, I
always carry my balanced cable and matching transformer as back up ...better to have and not "need" than to need and not have, right? I hope what I've said doesn't complicate things; just offering my perspective. If there's a simple take away from all this it is that the ES is a great system that not only works and sounds excellent, it provides one options that help anyone playing live get the most out of their guitar.
Edward