I haven't been back to this site in a while since buying a Dodge Charger SRT8 7 months ago. From the price side, you can get a lot of deals on SRT8s, so I got mine for roughly the same price as I would have paid for a SS. Also, the regular SRT8 comes with everything you would need (heated and cooled seats, heated steering wheel, heated cup holders, NAV, etc).
For me, I needed a four door car 7 months ago, so I wasn't able to wait to compare it to the SS. I do think the interior of the SS looks nicer than the Charger. The seats in the Charger SRT8 are really nice though.
From a speed perspective, I think that the Charger SRT8 is faster stock for stock. You can also tune them now, but it doesn't seem like the aftermarket is there like it will be for the SS. You can get tune and exhaust easily, but not sure what else. For me, the Charger SRT8 is fast enough. I have seen some guys on the forums running right at 12.1 with a tune, CAI on the Charger SRT8.
I do generally prefer GM products though, so after I have the SRT8 for a while, I will probably get a SS if they ever put the new Vette engine into it.