It's a never-ending debate. Both have their own pros and cons. I've experienced both active and passive 3D technology. Not much of a difference, atleast for me.
3D technology is not mainsteam yet. If we talk about the future of the 3D technology, glassless 3D seems to be the future. May be, it'll be time to upgrade our TVs (with latest tech) by the time 3D becomes mainstream. So we should not worry much about it as of now. We should just focus on getting a TV with good 2D picture quality and value for money.