I too learned outside rolling circles and later outside rolling harriers first. I find them easier because if you are going fast and you get a little late on the sticks you end up gaining altitude on the outside ones. If you are rolling in and the plane gets ahead of you lose altitude, inducing panic and then who knows what . My biggest suggestion would be to give the inputs just a little faster than you think you need to. I felt a little rushed on elevator and rudder at first trying to maintain altitude. This is for fast rollers, 4 or more in a circle. Doing 1 roll circles to the inside is really not too much different to me.