I agree, best to try some out and figure out what you like. If you're mostly riding street, you may like something with some nice high volume, puncture resistant balloon tires instead (they'd work really well to absorb curbs and potholes), or something else completely. Suspension may not be the thing for you if you're not interested in technical riding.

Good (front suspension, at least) won't rob you of much energy at all, some are available with a lockout now which will allow you to make the shock rigid on demand, allowing you a choice based on your terrain. I have a suspension fork on my commuter (which also does all my cross country), with its setup its still highly energy efficient, but the biggest downside to me is its need to be maintained moderately often - whereas a rigid fork needs nothing (or maybe a rust coating or something, but nothing you do often)