LCD. I've had a normal 50Hz (40") Sony LCD for almost 6 months now, and it has worked out very well. It's pointless getting a 720p plasma, when for the same price you can get a 1080p LCD (for me, anyway).
When I was researching this LCD vs Plasma thing last December, internet forums were full of LCD's motion lag, viewing angles or blacks. To be honest, I haven't even noticed motion lag. I mean, if I look out for it on some football matches, then sure (and it could just be a shitty source that creates the lag). For games or movies, it isn't an issue at all.
As far as the blacks go - LCD's are worse if you compare it to a decent plasma. I was watching TDK on a friends 720p LG plasma, and I wasn't impressed.
Then you also have the problem of Image Retention (not to be confused with burn-in) on Plasma's. It will happen, either with a games HUD or a channel logo, provided you've been on it for some time.
Anyhoo, go down to a showroom and see what you want. Your opinion may be different. But for the love of god, don't pick a lower end 720p plasma over a decent 1080p LCD if they are in the same price range.