I also have the Phil & Teds Dash. It's a great stroller and I use it with both my girls. I haven't seen the other jogger - it'd be worth having a look at both if you can and wheeling them around to see what you like best.
The P&T does sometimes feel a bit unsteady to me - there were times going over big bumps that I knew if I hadn't have had a good hold on the stroller it would've tipped. But I can't think of a situation where I wouldn't have had a good hold on it. And for level ground I find it absolutely super and it steers like a dream.