There's no real benefit to downgrading, you aren't going to get to 4.5. Staying on 9.0 is good enough and just live with the OOT exploit. There may/will be another N3DS exploit in the future for 9.0 users. Gateway would have mentioned downgrading to 4.5 and even explained it's benefits.
Just a tip for the OP. Don't feel safe just yet on your backup copy through gateway. If you have a hardmod do it that way also. The reason I say this is that the 3.1 may not be fully tested as we can see from the exploit. So don't do anything crazy just yet or you may regret it later.