If your previous experience was with bigger nitro powered helis, I think that you are going to be in for a shock with the smaller, twitchier T-Rex 450 line. Moving up from smaller helis is easy. Moving down is a real challenge.
I highly recommend that you go with the SE. This is simply the best behaved 450. Put flybar weights on to dampen down the cyclic response, use training gear to more safely get a feel for the quick response, and have at it.

Yes, this means upgrading your budget a bit. But if you go for a lower end model, on top of the decrease in stability that comes with the decrease in model size, I think that you will be disappointed.

Vince