Frankly, SPD are much better pedals for stop-and-go traffic than any of the road bike pedals. For one, you can clip in on either side and, two, the typical MTB shoes used with SPD pedals have lugged rubber soles that grip the pedal even if you miss the clip-in. If you miss the clip-in on SPD-SL, the slick hard sole shoes slip right off.

As far as getting out of SPD-SL pedals, twist your heel out and pull up. You may have to be more aggressive than with your SPD pedals but it's no big deal.