There's a reason why the pros no longer use toe clips and straps.
The technique involves coming into T2 already OUT of your cycling shoes and pedaling with your feet ON TOP of them. That's why on TRI specific cycling shoes they have one big strap -- you reach down, loosen and coast in. You just hop of the bike leaving your shoes clipped in and run into T2 barefoot/socked, drop the helmet, rack your bike and slip on your running shoes. SPD's or any clip in are better than toe clips and straps by 6% efficiency-wise. If you average 12 MPH in toe clips, it means you can average 13MPH in SPD's.
At your level, use what you've been training with -- I've used SPD's for sprints - iron distance. My SPD's aren't tri-specific and have 3 straps (hey, can't go wrong really for $30 Pearl Izumi's and at my level, 30 seconds doesn't matter much. You save more time by NOT wearing cycling gloves and having a good equipment layout.
Training for full distance triathlons.