I use both. I have Holdfast on my fixed gear and clips & straps on my road bike. They both give excellent power transfer. Additionally, the comfort provided by the wide strap on the Holdfast makes them more of a pleasure to use.

They are equal on power transfer and easy of entry, IMO. The difference is comfort, cost, and pedal compatibility.

Holdfast are for platform pedals, be they BMX style or Standard Track (not Pro Track) style. You don't have to use BMX pedals to use Holdfast. In fact, I don't recommend BMX pedals at all. To each their own, though...

Clips and straps are for Pro Track and racing/quill pedals. You can get much lighter pedals when you go for clips and straps. On a road bike, that's what people care about: how light things are. I don't use clipless because of my own personal reasons such as not liking the shoes and preferring to pull out by moving my foot backwards instead of to the side. However, I have been eyeing some Crank Brothers clipless pedals...

I have been riding both for months now (clips & straps for years), and am happy with both. I stand by Holdfast for fixed gear riding, and clips & straps for road bike riding. Still, I recognize that there is some personal decision making going on, too.