Keith posted a great graphic here somewhere as to proper wheel positioning on the front roller, If you've hit that sweet spot with your Tracker, then I can imagine the longer wheelbase would make it feel like you were being pulled around. As well if you turned the bars it would totally feel like you were going to go for a tumble.

The control seems better on the tighter bike at reasonable speeds, though I bet you wouldn't want to descend a mountain on a track geometry, it would feel full on squirrelly.