A guitar is worth what you are prepared to pay for it and no more... virtually anything with six strings on from Gibson is a well made instrument though as a rule the Studio models aren't considered as desirable as the Custom or Standard models (which are the ones that we normally see Edge and other worthies using) and therefore don't tend to hold their values as well as the other ones do, i.e. you might find it hard to sell it if you decide that you've gone off it. I have not heard this claim that Gibsons made after 2000 are no good and suspect that this is a marketing tactic to sell you something the seller won't otherwise shift for the above reason. SGs are hard to shift too, in fact I would suggest that anything by Gibson but the Les Paul Standard and Custom models would probably prove to be poor investments, assuming you ever decided to sell your purchase.
I think the main thing to bear in mind is that, regardless of the guitar, Edge sounds like Edge because, well, he is Edge. He has dozens of guitars so, even if the guitar itself is key to the sound, which I don't think is the case, your buying any particular one won't give you more than say a quarter at most of the sounds Edge gets and I have no doubt that he would still sound like Edge even if he was playing a cheap, made-on-Friday-afternoon plywood Chinese Fender Squier. What this boils down to is that the sound is 99% in your fingers, not the wood, so buying a guitar that Edge uses because you think that you will sound like Edge as a result is a sure path to disappointment (unless of course you are already very accomplished as a player, in which case you would not need to seek our advice, right?). Bear in mind that Edge has been playing since he was 12 or whatever so he has 30 + years of experience. Personally I'd recommend a Tele every time to a new guitarist because they have a nice slim neck so are easy for learners, simple electrics so no fooling about with multiple controls, are built to last and finally *always* sound great. They don't normally have a tremolo bar either which is a good thing in my opinion since this will generally screw up your tuning and most of the time use of the whammy is superflous/excessive anyway (unless you're Hank Marvin or Eddie Van Halen). Actually I'd recommend a Tele to virtually any guitarist of any ability. Edge does use Teles occasionally if that helps (I think he used one for SBS on the last tour and also for the Vertigo vid) but I'd suggest you go out without money (very important) and have a look at a load of guitars of whatever sort takes your fancy. If you have a knowledgable friend I'd take him or her along too. Remember, in the end a guitar is just a piece of wood; it's the skill of the guitarist that makes it sound great.