Since you have the choice, I'd absolutely agree with the last two posts... go with a 4 stroke for this plane. I'm running a Magnum 91 RFS in my Twist, swinging a 15x4W prop, and it is a fantastic combination.

For learning 3D, you just can't beat a 4 strokes ability to provide quick throttle response, swing nice big props, and make the maximum use of that little tank you get with the Twist. Plus, they just sound so cool!

If cost is an issue, you can sometimes pick up a Magnum 4 stroke for not much more than a comparable 2 stroke if you keep an eye peeled for sales and specials at Hobby People (I picked my 91 for just $139). Regardless of what you may read, the Magnum RFS 4-strokes are great engines and a real bargain.