I'm not as expert as a lot of guys on here but I can give you an opinion. I think for a small lift spacers are good value. I had a 2" OME lift on my old Cherokee, and I just fitted a Rubicon Express BB (1.75" spacers with shocks) on my TJ. A spring lift feels a bit more like doing the job properly and if I'd had the budget at the time I would have probably gone for OME again, but for less than half the money (and these things are really expensive over here) I think the spacer kit does a great job. I plan to go a bit higher next year and that will be a spring lift without a doubt.
Not much science I'm afraid, but just an opinion.