Re: Jackson Dinky std. vs Ibanez Rg 550
I'm assuming by Dinky Standard, you are talking about something like a DK2 series. If it is a used DK1, they really are even, but those generally aren't very common, at that level they pretty much just make Soloists.
Upper fret access is a bit worse on a Dinky, assuming you are comparing to an RG-550 with a block heel, much worse if compared to an AANJ RG. An Edge it a better tremolo than the licensed one on the DK2's, but since the RG-550 is used, the amount of wear and tear on it could be a factor. Sound is going to be subjective, both come with fairly solid pick-ups. That level of Ibanez guitar does feel a bit better made, as well.
Personally, I would say the RG-550 over the Jackson DK2 in most cases. Now if you save up a bit more, a Jackson Soloist might be a good option if you want a neck through. It is a fairly close thing though. I've played on both and if I had to get something in that price range other than an RG, a Dinky would definitely be a pretty high choice.