Sounds like a fair trade. The Gibson is the better guitar in my opinion, but take whichever one you like better.
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"A person is a success if they get up in the morning and gets to bed at night and in between does what he wants to do."
Basically you're only gaining a tremolo system, which is not top of the line and will require learning to tune properly and losing a lot of what your Gibson is. Myself, I couldn't justify the $250 and entry level guitar and suggest you take chances to play the RG a lot more before making any trade.
Unless you really dislike your SG and want a hair-metal guitar with a tremolo system there’s not much point. My guess is that your friend wants to be rid of that Edge III tremolo and is hoping you don’t know how annoying they can be when they aren’t working right.
Is there any other way you could come across the money you owe this other guy?
maybe an entry level guitar of yours could be sold instead or poke' man cards?

if you have that many guitars and half of them have a tremolo system, what is so fascinating about the ibanez besides the color scheme and fret inlays?
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Hmm ,well i like how it looks white with the pearl pickguard remind me of the JEM which i want.. hah.

But the thing is that i'd rather sell or trade my gibson to a friend than some stranger or noobie kid whos going to torture it.

or would i make more money off it if i sell it locally like say craigslist?