I bought my first clipless set-up off craigslist for $50. It included Shimano RD-76 road shoes, Shimano mtb pedals & cleats, all in good condition. Eventually I bought a road bike that came with 105 pedals. So I bought some road cleats and switched them to the Rd-76 shoes and bought some mtb casual type shoes for $20 from nashbar to switch over to the fixed gear.

What I'm getting at is that I got 2 bikes worth of clipless setups for <$100. If you search ebay and craigslist you can find used stuff for pretty cheap.

I prefer clipless over clips/straps just because it's so much more efficient. But for beginners I think a clips/straps setup with track pedals is the way to go, especially on conversions. My brother for instance just got his first fixed gear and it's a conversion with 175mm cranks, due to potential pedal strike it's best to have a narrow pedal.

Plus BMX pedals look so ****ing stupid.

Also, I would regularly tighten down my straps while riding when I still rode clips/straps, though I admit, I did it a lot more when I used nylon straps because it's so much easier with them.